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GENERAL  SPECIFICATIONS 


FOR 


CONCRETE  BRIDGES 

BY 
WILBUR  J.WATSON 

.  Mem.  Am.  Soc.  G.  E. 


THIRD  EDITION 


1916 


Copyright,  1916,  by 

WILBUR  J.  WATSON 

1150  Leader  Building 

CLEVELAND,  OHIO 


FOR  SALE  BY 

McGRAW-HILL  BOOK  COMPANY,  Inc. 

239  West  39th  Street 
NEW  YORK  CITY 

Price,  $I.OO 


GENERAL  SPECIFICATIONS 


FOR 


CONCRETE  BRIDGES 

BY 

WILBUR  J.  WATSON 

Mem.  Am.  Soc.  G.  £. 


THIRD  EDITION 


"Bridges  ought  to  have  the  self- 
same qualifications  we  judge  neces- 
sary in  all  other  buildings,  which 
are,  that  they  should  be  commodi- 
ous, beautiful  and  lasting." 

— ANDREA  PALLADIO. 


Preface 

The  first  edition  of  these  specifications  was  published  in  1908  and  the  second  in  1910.  In 
order  to  bring  this  edition  up  to  date,  it  has  been  found  necessary  to  make  some  radical  changes 
in  the  requirements,  particularly  in  the  section  devoted  to  the  Quality  of  Materials.  The  sections 
on  Surface  Finish  and  Waterproofing  have  been  completely  rewritten.  It  is  in  the  branches  of 
the  Art,  covered  by  these  three  sections,  that  the  greatest  advancement  has  been  made  in  the  past 
six  years. 

The  two  previous  editions  have  been  widely  used  by  designing  engineers  for  railroads,  cities 
and  counties,  and  as  a  standard  basis  for  the  preparation  and  comparison  of  competitive  designs. 
It  is  hoped  that  the  present  edition  will  be  found  to  be  even  more  valuable  for  these  purposes. 

The  value  of  concrete  and  reinforced  concrete  as  a  material  of  construction  has  been  firmly 
established  during  the  past  decade,  as  has  also  the  necessity  for  careful  design,  selection 
of  materials  and  execution.  Practically  all  of  the  troubles  and  failures  which  have  occurred 
could  have  been  avoided  by  the  careful  observance  of  specifications  such  as  are  given  herein. 

Cleveland,  Ohio,  January,  1916.  WILBUR  J.  WATSON. 


341733 


Index  to  Sections 


PAGE 

Section  I.  Definitions,  Classification  and  Loads 5 

"  II.  Rules  for  Computing  and  Designing 8 

"  III.  Working  Unit  Stresses 12 

"  IV.  Formulas  15 

"  V.  Quality  of  Materials  for  Concrete  Work 22 

"  VI.  Proportioning,  Mixing  and  Placing  Concrete 25 

"  VII.  Requirements  for  Placing  Reinforcing  Steel,  Inserts,  etc 29 

"  VIII.  Placing  Concrete  in  Cold  Weather 31 

"  IX.  Forms  and  Centers 32 

"  X.  Surface  Finish 34 

"  XL  Waterproofing 36 

"  XII.  Reinforced  Steel  Construction 40 

"  XIII.  Cast  Stone  and  Blocks 42 

"  XIV.  Concrete  Piling 44 

"  XV.  Inspection  and  Tests 46 

"  XVI.  Retaining  Walls,  Abutments,  Piers,  etc 47 

"  XVII.  Concrete  Arches  49 

"  XVIII.  Reinforced  Concrete  Slabs,  Beams,  Girders,  Columns  and  Trusses 51 

XIX.  Foundations  and  Footings  52 

"  XX.  Timber  Piling  54 

"  XXL  General  56 

XXII.  Cement  Walks,  Concrete  Curbs  and  Roadways 57 

"  XXIII.  Brick  Pavement  60 

"  XXIV.  Asphalt  Block  Pavement 62 

"  XXV.  Sheet  Asphalt  Pavement 64 

"  XXVI.  Wood  Block  Pavement 66 

XXVII.  Bituminous  Pavement  .  69 


Watson's   Bridge   Specifications  Section  I 


Definitions,  Classification  and  Loads 


1.  CONCRETE  is  defined  as  a  structural  material  composed  of  a  mixture  of  coarse  and 
fine  aggregates,  with  a  cementing  material,  the  latter  being  assumed  to  be  Portland  Cement,  unless 
otherwise  specified. 

2.  MASS  CONCRETE  is  defined  as  concrete  containing  no  steel  reinforcement  to  assist 
in  resistance  to  stress. 

3.  Mass  concrete  may  contain  dowels,  anchors  or  ties. 

4.  RUBBLE  CONCRETE  is  defined  as  concrete   containing  large   embedded   stone,   and 
may  be  used  where  very  large  masses  of  concrete  are  required. 

5.  REINFORCED  CONCRETE  is  defined  as  concrete  containing  reinforcing  members  of 
steel,  so  placed  as  to  provide  the  necessary  resistance  to  tensile  stresses,  and  to  assist  in  the  resist- 
ance to  shearing  (web  stresses)  and  compressive  stresses  when  required. 

6.  Reinforced  concrete  is  divided  into  two  sub-classes : 

(a)  MONOLITHIC  CONSTRUCTION  or    concrete  moulded  in  place,  and 

(b)  UNIT  CONSTRUCTION  or  concrete  not  moulded  in  place  but  put  together  in  units, 
such  as  structures  consisting  of  slabs,  beams,  girders  and  columns  manufactured  in  a  factory  or 
yard  and  erected  in  place. 

7.  CAST  STONE  work  will  include  cast  concrete  facing  blocks,  railings  and  ornamental 
work  constructed  of  separately  moulded  and  cast  blocks  of  concrete. 

8.  Concrete  Bridges  are  divided  according  to  use  into  the  following  classes : 
Class  A — Heavy  Railroad  Bridges. 

"      B— Light  Railroad  Bridges. 

C — Heavy  Electric  Railway  Bridges. 
"      D — Light  Electric  Railway  Bridges. 

"      E — City  Highway  Bridges  carrying  Electric  Railway  Tracks. 
"      F — City  Bridges  without  Electric  Railway  Tracks. 
"      G — Suburban  Bridges  carrying  Electric  Railway  Tracks. 
"      H — Suburban  Bridges  without  Electric  Railway  Tracks. 

I  — Light  Country  Bridges. 
"      J — Foot  Bridges. 

9.  Concrete  Bridges  are  divided  according  to  design  into  the  following  types : 

(1)  Circular  and  Box  Culverts.  (5)  Arch  Bridges. 

(2)  Slab  Bridges.  (6)  Cantilever  Bridges. 

(3)  Deck  Beam  Bridges.  (7)  Truss  Bridges. 

(4)  Through  Girder  Bridges.  (8)  Viaducts. 

10.  Bridges  will  be  designated  by  reference  to  class  and  type ;  thus  a  city  highway  arch  of 
60  foot  span  and  carrying  electric  railway  tracks,  should  be  designated  as  a  Class  E  Arch  Bridge. 

11.  Class  A  Bridges  shall  be  designed,  unless  otherwise  specified,  for  Coopers  EGO  loading 
and  shall  be  used  for  all  railroads  carrying  heavy  traffic,  hauled  by  locomotive  power. 


Watson's   Bridge    Specifications  Section  I 

12.  Class  B  Bridges  shall  be  designed,  unless  otherwise  specified,  for  Coopers  E40  loading 
and  shall  be  used  for  railroads  carrying  light  traffic,  hauled  by  locomotive  power. 

13.  Class  C  Bridges  shall  be  designed,  unless  otherwise  specified,  for  two  100  ton  (200,000 
Ib.)   cars  entrain,  wheel  base  6  feet,  22  feet  center  to  center  of  trucks,  and  shall  be  used  for 
electric  railways  carrying  very  heavy  traffic. 

14.  Class  D  Bridges  shall  be  designed,  unless  otherwise  specified,  for  two  50  ton  (100,000 
Ib.)    cars   entrain,   wheel   base   G   feet   22   feet  center  to  center  of  trucks,  and  shall  be  used  for 
electric  railways  carrying  light  traffic. 

15.  Class  E  Bridges  shall  be  designed  for 

(a)  A  concentrated  live  load  of  24  tons  (48,000  Ibs.)  on  two  axles,  12  foot  centers 
and  6  foot  gauge,  assumed  to  occupy  a  space  10  feet  wide  by  30  feet  long  ;  and 

(b)  A  uniformly  distributed  load  of  100  Ibs.  per  square  foot  on  all  roadways  and  foot- 
walks. 

(c)  The  street  railway  tracks  shall  be  assumed  to  carry  the  loads  specified  for  Class  D 
Bridges. 

16.  Class  F  Bridges  shall  be  designed  to  carry  the  concentrated  and  uniformly  distributed 
live  loads  as  given  for  Class  E. 

17.  Class  G  Bridges  shall  be  designed  to  carry  a  concentrated  live  load  of  18  tons  (36,000 
Ibs.),  and  a  uniformly  distributed  live  load  of  100  Ibs.  per  square  foot  of  roadways  and  foot- 
walks  arranged  as  for  Class  E  Bridges.     The  street  railway  tracks  shall  be  assumed  to  carry  the 
loads  specified  for  Class  D  Bridges. 

18.  Class  H  Bridges  shall  be  designed  to  carry  a  concentrated  live  load  of  15  tons  (30,000 
Ibs.)  and  a  uniformly  distributed  live  load  of  100  Ibs.  per  square  foot  arranged  as  for  Class  E. 

19.  Class  I  Bridges  shall  be  designed  to  carry  a  concentrated  live  load  of  12  tons  (24,000 
Ibs.)  and  a  uniformly  distributed  live  load  of  75  Ibs.  per  square  foot  arranged  as  for  Class  E. 

20.  Class  J  Bridges  shall  be  designed  for  a  uniformly  distributed  live  load  of  75  Ibs.  per 
square  foot. 

21.  Bridges  designed  for  other  loads  than  given  herein  shall  be  classed  special  and  that  letter 
shall  be  used  to  designate  them  which  is  used  herein  to  represent  that  class  to  which  they  most 
nearly  conform;  thus  an  electric  railway  bridge  designed  for  60  ton  cars  should  be  designated 
as  Special  Class  D. 

22.  An  addition  shall  be  made  to  all  stresses  caused  by  concentrated  live  loads  to  cover  the 
effects  of  impact,  vibration,  etc.,  which  shall  be  determined  in  the  following  manner: 

For  Classes  A  and  B,  Impact  =  S  L^?800>  and  for  Classes  C  and  D,  Impact  =  S 
For  all  other  Classes,  Impact  =  S 


where  I  =  impact  to  be  added  to  the  live  load  stress, 

S  =  calculated  maximum   live   load  static  stress, 

L  =  length  of  loaded  distance  in  feet  which  produces  the  maximum  stress  in  the  member. 

6 


Watson's   Bridge    Specifications  Section  I 

23.  The  above  impact  formulas  are  to  be  used  without  reduction  when  the  concentrated 
loads  are  carried  directly  upon  the  structure  and  pass  over  same  at  full  speed.     When  there  is 
provided  a  cushion  of  sand,  6  inches  or  more  in  thickness,  or  an  equivalent  cushion  between  the 
pavement  or  ties,  which  carry  concentrated  loads,  and  the  structure  itself,  the  impact  stresses  may 
be  reduced  20  %,  and  10  %  additional  for  each  additional  foot  of  such  earth  or  sand  cushion. 

24.  For  Classes  A,  B,  C  and  D,  the  amount  of  impact  may  be  reduced  for  structures  carry- 
ing sidetracks,  or  other  locations  that  do  not  permit  the  passage  of  loads  at  high  speed,  the  amount 
of  reduction  to  be  determined  by  the  Engineer  in  charge  for  each  case. 

25.  When  the  live  load  stress  is  of  an  opposite  sign  to  the  dead  load  stress,  then  the  impact 
shall  be  assumed  to  be  in  all  such  cases  equal  to  the  live  load  stress,  and  in  case  of  reversal  of 
stress  by  live  load  the  member  shall  be  proportioned  for  a  stress  equal  to  the  sum  of  the  greater 
and  one-half  the  lesser  maximum  stresses. 

26.  Wind  pressure  shall  be  assumed  at  50  Ibs.  per  square  foot  on  the  greatest  vertical  pro- 
jection of  the  structure  unloaded  for  all  classes,  and  30  Ibs.  per  square  foot  on  the  same  surface, 
plus  400  Ibs.  per  lineal  foot,  applied  7  feet  above  the  rail  for  Classes  A,  B,  C  and  D,  when  loaded, 
the  load  being  assumed  to  weigh  1,200  Ibs.  per  lineal  foot. 

27.  Classes  A,  B,  C  and  D  Bridges  shall  be  computed  for  a  lateral  force  of  200  Ibs.  per 
lineal  foot  plus  10%  of  the  specified  train  load  on  one  track,  these  forces  being  considered  as 
moving.    The  lateral  force  shall  be  used  for  lateral  systems  only  and  shall  be  considered  as  re- 
placing the  wind  load  given  above,  when  giving  larger  stresses. 

28.  When  the  structure  is  on  a  curve  the  Centrifugal   Force   shall   be  considered   and  cal- 
culated, for  all  classes  carrying  tracks,  by  the  formula 

C  =  0.03  W  D  for  curvature  up  to  5°  D  =  degree  of  curvature 

Where  C  —  Centrifugal  force  in  pounds  W  —  weight  of  train  in  pounds 

The  co-efficient  for  centrifugal  force  (0.03)  shall  be  reduced  0.001  for  every  degree  of  curva- 
ture above  5°. 

29.  The  effect  of  suddenly  stopping  the  moving  load  shall  be  considered  the  co-efficient  of 
friction  of  wheels  sliding  upon  the  rails  being  assumed  at  0.2. 


Watson's  Bridge   Specifications  Section  II 

Rules  for  Computing  and  Designing 


WEIGHTS. 

1.  The  weight  of  Tracks  (Rails  and  Ties)   shall  be  taken  at  250  Ibs.  per  lineal  foot  for 
ballasted  construction,  and  400  Ibs.  per  lineal  foot  for  timber  deck  construction. 

2.  The  weight  of  Ballast  for  Classes  A,  B,  C  and  D  shall  be  assumed  at  1,200  Ibs.  per  lineal 
foot  of  track  with  sub-grade  21  inches  below  top  of  rail  and  14  feet  wide  for  single  track  and 
27  feet  wide  for  double  track. 

LIVE  LOAD  DISTRIBUTION. 

3.  Concentrated  axle  loads  from  locomotive  and  motor  wheels  may  be  considered  as  dis- 
tributed over  a  length  of  rail  equal  to  5  feet.     The  lateral  distribution  may  be  assumed  to  be 
equal  to  the  gauge  of  track,  plus  3  feet,  plus  twice  the  value  of  d2,  (See  Section  IV)  but  shall  not 
exceed  the  spacing  of  the  tracks. 

4.  When  tracks  are  carried  on  a  fill  of  4  feet  or  more  over  concrete  slabs  or  arches,  the 
lateral  distribution  may  be  assumed  as  equal  to  the  track  spacing  or  as  equal  to  14  feet  in  the  case 
of  single  track. 

5.  Concentrated  loads  on  reinforced  concrete  slabs  may  be  assumed  to  be  distributed  over 
a  distance  of  4  feet  at  right  angles  to  the  supports,  and  a  distance  equal  to  2  feet  plus  3/10  L, 
parallel  to  the  supports  where  L  =r  the  clear  span  of  the  slab  between  main  supports.  For  panels 
supported  on  four  sides,  when  the  long  side  does  not  exceed  by  more  than  25%  the  short  side, 
the  load  may  be  assumed  to  be  distributed  in  both   directions   a   distance   equal   to   2    feet  plus 
3/10  L. 

6.  In  the  case  of  stringers  for  highway  bridges  and  similar  construction,  the  maximum  con- 
centrated loads  on  any  stringer  shall  be  assumed  to  be  the  total  concentrated  load  which  can  be 
placed  directly  over  that  stringer,  multiplied  by  the  distance  between  the  stringers,  and  divided 
by  the  gauge  or  distance  apart  (measured  at  right  angles  to  the  line  of  the  stringers)  of  the  con- 
centrated loads. 

LENGTH  OF  SPAN. 

7.  The  length  of  span  for  reinforced  concrete  slabs,  beams,  girders  and  trusses,  when  com- 
puted as  simple  beams,  shall  be  considered  to  be  the  clear  distance  between  supports.    When  com- 
puted as  continuous  or  fixed  beams,  the  length  of   span   shall  be  considered  to  be  the  distance 
between  centers  of  support. 

8.  All  slabs,  beams  and  girders  of  monolithic  construction  shall  be  considered,  unless  other- 
wise shown  on  the  drawings,  to  be  partially  continuous  and  shall  have  reinforcement  in  the  upper 
part  of  the  beam  at  the  supports.    Provision  for  taking  care  of  stress,  due  to  negative  moment 
over  the  supports,  shall  never  be  omitted,  unless  such  slabs,  beams  and  girders  are  so  detailed 
that  they  cannot  act  as  continuous  beams. 

9.  The  theoretical  length  of  span  for  arches  shall  be  considered  to  be  equal  to  the  span  of 
the  neutral  axis  of  the  arch  ring. 

10.  The  theoretical  rise  of  arches  shall  be  assumed  to  be  the  distance  from  the  line  con- 
necting the  ends  of  the  neutral  axis  to  the  neutral  axis  at  the  crown. 

11.  The  above  definitions  for  span  and  rise  of  arches  are  for  computing  purposes  only; 
the  actual  span  and  rise  shown  on  construction  drawings  shall  be  the  clear  span  between  spring- 
ing lines  and  the  clear  rise  to  the  intrados  of  the  arch. 

8 


Watson's  Bridge   Specifications  Section  II 

MOMENTS. 

12.  For  simple  beams,  the  bending  moments  due  to  external  forces  shall  be  determined  by 
the  usual  methods ;  and  for  partially  continuous  or  restrained  beams,  the  maximum  positive  bend- 
ing moment  shall  be  taken  at  8/10  the  corresponding  moment  as  determined  for  simple  beams, 
and  the  maximum  negative  moment  at  intermediate  supports  shall  be  taken  at  not  less  than  % 
the  maximum  positive  moment,  and  at  end  supports  at  not  less  than  %  the  maximum  positive 
moment.    The  above  requirement  is  intended  to  apply  to  the  usual  "T"  beam  construction.  When- 
ever it  is  practicable  to  determine  more  exactly  the  maximum   positive   and  negative  moment, 
such  determination  shall  be  made. 

13.  In   proportioning   columns,    the   effect  of  eccentric  loading  shall  be  taken  fully  into 
account,  whether  said  eccentricity  be  caused  by  unbalanced  or  unequal  loading  or  by  details  of 
construction. 

THEORETICAL  ASSUMPTIONS. 

14.  All  tensile  stresses  shall  be  considered  to  be  resisted  by  the  steel  reinforcement;  no 
allowance  shall  be  made  for  concrete  in  tension. 

15.  The  stress-strain  curve  of  concrete  in  compression  shall  be  assumed  to  be  a  straight  line. 

16.  The  Modulus  of  Elasticity  of  concrete  shall  be  taken  as  2,000,000  Ibs.  per  square  inch 
(  =  1/15  that  of  steel)  for  1-2-4  (No.  6)  concrete  having  an  ultimate  strength  at  60  days  of 
2,000  Ibs.  per  square  inch,  or  less;  2,500,000  (  —  1/12  that  of  steel)   for  l-iy2-3   (No.  4i/2)  con- 
crete having  an  ultimate  strength  between  2,200  and  2,400;  and  3,000,000  (  =  1/10  that  of  steel) 
for  1-1-2  (No.  3)  concrete  having  an  ultimate  strength  in  excess  of  2,400  Ibs.  per  square  inch. 
These  modulii  shall  be  assumed  to  be  constant  within  the  limits  of  the  allowable  range  of  stress. 

17.  A  plane  before  bending  shall  be  assumed  to  remain  a  plane  after  bending. 

18.  Initial  stresses  in  concrete  and  steel  due  to  shrinkage  of  concrete  in  setting  shall  be 
neglected. 

"T"  BEAMS. 

19.  In  the  computation  of  the  resistance  of  "T"  beams,  the  portion  of  the  slab  that  may  be 
assumed  to  assist  in  compression  shall  be  limited  so  that  in  no  case  shall  the  projecting  part  of 
the  slab  portion  exceed  in  width  four  times  the  thickness  of  the  slab,  and  the  total  top  width  shall 
not  exceed  three  times  the  thickness  of  the  stem,  or  one-fourth  the  span  of  the  slab  or  of  the  beam. 

20.  When  the  thickness  of  the  slab  portion  is  less  than  .35  the  total  depth  of  the  beam,  the 
increased  compression  in  the  slab  shall  be  taken  into  account,  and  the  ratio  of  steel  area  in  tension 
to  the  area  of  the  enclosing  concrete  rectangle  shall  be  reduced.     (See  Table,  page  21). 

21.  When  the  thickness  of  the  slab  portion  of  a  "T"  beam  is  less  than  one-fifth  the  depth  of 
the  stem,  fillets  shall  be  used  at  the  juncture  of  slab  and  stem,  the  thickness  of  which  at  the  stem 
shall  be  not  less  than  one-fifth  the  depth  of  the  stem,  and  such  fillet  shall  extend,  when  possible, 
to  the  limits  of  the  slab  portion  of  the  "T"  beam.    The  slab  part  of  the  "T"  beams  shall  be  placed 
at  the  same  time  and  be  composed  of  the  same  materials  and  class  of  concrete  as  the  stem. 

22.  In  designing  partially  continuous  "T"  beams  the  compression  in  the  lower  portion  of 
the  stem  at  point  of  maximum  negative  moment  shall  be  computed  and  if  it  exceeds  the  maximum 
allowable  unit  stress  on  concrete,  sufficient  compressive  reinforcement  shall  be  provided. 

WEB  REINFORCEMENT. 

23.  Whenever  the  unit  web  tensile  stresses  on  concrete  exceed  the  allowable  unit  stresses, 
as  given  in  Section  III,  steel  stirrups  shall  be  used  to  provide  for  the  excess  tensile  stresses  or 
part  of  the  rods  shall  be  bent  up  in  such  a  manner  as  to  provide  the  necessary  resistance,  but  in 


Watson's   Bridge    Specifications  Section  II 

the  latter  case,  care  shall  be  taken  to  leave  enough  rods  in  the  lower  portion  of  the  beam  at  the 
ends  to  provide  the  adhesion  required  to  develop  the  tensile  stress  at  any  point,  and  if  necessary, 
the  straight  bars  shall  be  anchored  at  the  ends. 

24.  In  no  case  shall  flange  reinforcement  be  assumed  to  assist  in  the    resistance    to    web 
stresses. 

25.  In  reinforcing  to  provide  resistance  to  web  tension,  diagonal  bars,  rigidly  attached  to  the 
main  reinforcing  bars  in  such  a  way  as  to  transmit  the   full  strength  of  the  web  bar  into  the 
main  bar  without  distortion  of  the  connection,  shall  be  preferred.    The  web  bars,  designed  in  this 
way  and  having  a  length  above  the  neutral  axis  sufficient  to  develop  the  full  strength  of  the  mem- 
ber by  adhesion  and  having  all  bends  of  a  radius  not  less  than  eight  times  the  side  or  diameter 
of  bar,  may  be  stressed  to  12,000  Ibs.  per  square  inch. 

26.  Vertical  stirrups  shall  pass  under  the  main  bars  or  be  rigidly  attached  thereto.   Stresses 
in  vertical  stirrups  shall  not  exceed  10,000  Ibs.  per  square  inch. 

27.  Web  reinforcing  bars  shall  be  spaced  a  distance  apart  not  exceeding  the  depth  of  the 
beam  from  the  compressive  surface  to  the  reinforcement  (d2)  for  diagonal  members  or  one-half 
this  distance  for  vertical  members  when  used  alone.    When  vertical  members  are  used  in  com- 
bination with  diagonal  members,  each  may  be  spaced  a  distance  apart  not  exceeding  d2. 

FOOTINGS. 

28.  In  computing  reinforced  concrete  footings,   the  combined  compressive   stress,  due  to 
bending  in  several  directions,  shall  not  exceed  the  allowable  unit  stress.     In  computing  shear- 
ing stresses,  the  column  load  may  be  assumed  to  spread  outward  from  the  base  of  the  column 
at  an  angle  not  greater  than  35°  with  the  vertical.     The  shear  along  this  35°   surface    shall    not 
exceed  the  allowable  unit  for  diagonal  tension  in  concrete.    The  load  carried  by  the  footing  area 
within  the  35°  planes  may  be  deducted  from  the  total  column  load  in  computing  this  shear. 

29.  All  reinforcing  bars  in  concrete  footings  shall  be  protected  with  not  less  than  2~y2  inches 
of  concrete. 

TEMPERATURE. 

30.  The  coefficient  of  expansion  of  concrete  due  to  temperature  changes  shall  be  assumed 
to  be  .0000055  per  degree  Fahrenheit. 

31.  A  range  of  temperature  from  +20°  to  -j-90°  Fahr.  shall  be  assumed  for  latitude  40°  and 
this  shall  be  increased  for  higher  latitudes  and  decreased  for  lower  latitudes.     Stresses  due  to 
temperature  will  be  combined  with  dead  and  live  load  stresses  to  obtain  maximum  unit  stresses. 

32.  In  computing  stresses  in  arches,  the  range  of  temperature  shall  be  assumed  at  -j-35° 
Fahr.  unless  otherwise  specified. 

SHRINKAGE. 

33.  The  coefficient  of  contraction  or  shrinkage  of  concrete  set  in  air  shall  be  assumed  at  .002 
divided  by  the  ratio  of  the  amount  of  aggregates  to  the  amount  of  cement  (  =  .002  divided  by 
number  of  mix). 

34.  The  contraction  or  shrinkage  of   concrete  set  in  air  shall  be  provided  for  by  proper 
details. 

35.  In  computing  stresses  in  arches,  the  effect  of  the  rib  shortening,  due  to  loads,  shall 
be  taken  fully  into  account,  but  the  effect  of  contraction  due  to  setting  may  be  neglected. 

10 


Watson's  Bridge   Specifications  Section  II 

LOADS  ON  CULVERTS. 

36.  The  pressure  of  earth  fill  over  the  tops  of  culverts  imbedded  in  earth  embankments  shall 
be  assumed  to  be  equal  to  the  total  weight  of  the  material  above  the  top  of  the  culvert  without 
any  allowance  for  arching  action. 

37.  The  lateral  pressure  on  the  side  walls  of  culverts  imbedded  in  earth  embankments  shall 
be  assumed  to  be  equal  to  25%  of  the  weight  on  the  top. 

GENERAL. 

38.  Rectangular  slabs  supported  on  four  sides  and  reinforced  in  two  directions  shall  be  pro- 
portioned on  the  assumption  that  the  loads  carried  by  the  two  systems  are  in  inverse  proportion 
to  the  fourth  powers  of  the  sides. 

39.  All  reinforcing  bars  shall  be  of  sufficient  length  to  develop  the  full  stress  in  the  bar  at 
all  points  without  exceeding  the  allowed  unit  stress  of  adhesion  of  concrete  to  steel,  or  proper 
anchorage  must  be  provided. 

40.  Care  shall  be  taken  to  insure  that  all  reinforcing  bars   over   supports    have    sufficient 
length  to  develop  their  computed  stress  by  adhesion. 

41.  A  bend  of  90°  or  more  at  the  end  of  a  bar  shall  be  considered  capable  of  developing  not 
more  than  one-half  the  tensile  strength  of  the  bar. 

NOTE: — Usually,  when  bars  are  anchored  at  the  ends,  the  stress  at  the  point  of  anchorage 
is  much  less  than  the  working  strength  of  the  bar,  the  greater  part  of  the  load  having  been 
already  relieved  by  adhesion,  and  a  radius  of  bend  of  3  inches  will  be  sufficient,  provided  that 
five-eighths  of  the  load  is  taken  care  of  by  adhesion. 

43.  Members  subject  to  combined  stresses,  such  as  a  combination  of  direct  compression  and 
compression  due  to  bending,  shall  be  so  proportioned  that  the  combined  stresses  shall  not  exceed 
the  allowed  maximum  stresses  as  given  in  Section  III. 

43.  Floor  systems  composed  of  reinforced  concrete  beams,  separated  by  tile  or  metal  fillers, 
shall  be  so  designed  that  no  reliance  is  placed  upon  the  tile  or  metal  fillers  for  strength. 

44.  All  calculations  shall  be  made  to  working  stresses  and  safe  loads  as  given  in  Section  III. 


11 


Wataon'i  Bridge   Specifications  Section  III 


Working  Unit  Stresses 


1.  The  unit  stresses  given  in  this  section  apply  only  to  concrete  of  the  mixtures  propor- 
tioned as  herein  specified  and  possessing  the  strength  specified  therefor.     For  mixtures  of  other 
proportions,  the  unit  stresses  used  shall  be  in  direct  ratio  of  the  strength  of  such  mixtures  to  the 
strength  of  the  standard  mixtures  as  given  in  Section  VI,  both  strengths  being  taken  at  sixty 
days. 

BEARING 

2.  The  bearing  of  masonry  plates  on  1-3-6   (No.  9)  concrete  shall  not  exceed  400  Ibs.  per 
square  inch;  on  1-2-4  (No.  6)  concrete  500  Ibs.;  on  1-1-2  (No.  3)  concrete  600  Ibs.,  and  the  area 
of  the  bearing  plate  shall  not  exceed  one-half  the  area  of  the  surface  receiving  said  plate. 

COMPRESSION 

3.  The  direct  compressive  stress  in  massive  concrete  shall  not  exceed  400  Ibs.  for  1-3-6 
(No.  9)  concrete  or  500  Ibs.  for  1-2-4  (No.  6)  concrete. 

4.  The  compressive  stress  in  reinforced  concrete  due  to  bending  shall  not  exceed  550  Ibs. 
per  square  inch  for  1-2^2-5  (No.  7^)  concrete  nor  700  Ibs.  per  square  inch  for  1-2-4  (No.  6) 
concrete,  when  determined  by  the  straight  line  formula. 

5.  The  maximum  allowable  stress  on  steel  in  compression,  when  not  otherwise  specified 
herein,  shall  not  exceed  the  maximum  co-existing  stress  in  the  contiguous  concrete  multiplied 
by  the  ratio  of  the  modulus  of  elasticity  of  the  steel  to  that  of  the  concrete.    See  Paragraph  9. 

COLUMNS 

6.  All  concrete  in  columns,  unless  otherwise  specified,  shall  be  1-2-4  (No.  6)  mix. 

7.  The  direct  compression  on  plain  concrete  columns  shall  not  exceed  300  Ibs.  per  square 
inch  and  the  length  of  such  columns  shall  not  exceed  six  times  their  least  side. 

8.  For  reinforced  concrete  columns,  whose  length  exceeds  twelve  times  the  diameter  or 
least  side,  the  unit  stresses  in  steel  and  concrete  shall  be  reduced  10%  for  each  additional  foot,  or 
fraction  thereof,  in  length  of  column. 

9.  The  direct  compression  on  concrete  columns,  reinforced  by  vertical  rods  only,  shall  not 
exceed  400  Ibs.  per  square  inch  on  1-2-4  (No.  6)    concrete  when  the   reinforcement  is  not  less 
than  ^2%  of  the  concrete  section,  which  is  the  minimum  amount  of  reinforcement  which  shall  be 
considered  in  a  reinforced  concrete  column.    All  columns  having  less  than  this  amount  shall  be 
assumed  to  be  plain  concrete  columns.    The  longitudinal  reinforcing  bars  shall  not  exceed  4%  of 
the  total  concrete  section,  and  shall  be  assumed  to  assist  in  carrying  the  direct  load  at  a  unit 
stress  of  10,000  Ibs.  per  square  inch.    The  unit  compressive  stress  on  concrete  shall  be  applied  to 
the  total  column  section,  no  deduction  being  made  for  the  area  of  the  reinforcement. 

10.  When  the  reinforcement  consists  of  vertical  bars  and  spiral  hooping,  the  concrete  shall 
not  be  stressed  more  than  650  Ibs.  per  square  inch  on  the  gross  area  within  the  hooping  for  1-2-4 
(No.  6)  concrete,  provided  that  the  amount  of  vertical  reinforcement  be  not  less  than  the  spiral 
reinforcement  nor  greater  than  5%  of  the  area  within  the  hooping;  that  the  percentage  of  spiral 
hooping  be  not  less  than  */*%  and  not  to  exceed  ^-l/2%  of  gross  area  within  the  hooping;  that 
the  pitch  of  the  spiral  be  uniform  and  not  greater  than  3  inches ;  that  the  spiral  be  properly  secured 

12 


Watson's  Bridge   Specifications  Section  III 

to  the  verticals ;  and  that  the  verticals  be  not  less  than  four  in  number  for  columns  having  cores  12 
inches  or  less  in  diameter,  nor  less  than  eight  for  larger  columns.  In  such  columns  the  vertical 
steel  may  be  assumed  to  assist  in  carrying  the  direct  load  at  a  unit  stress  of  10,000  Ibs.  per  square 
inch,  and  the  hooping  may  be  considered  as  equivalent  to  2  A  times  its  volume,  taken  as  vertical 
reinforcement. 

11.  When  a  mixture  of  1-1^-3  (No.  4^)   is  used  for  the  concrete,  the  unit  load  on  the 
concrete  core  may  be  taken  at  750  Ibs.  per  square  inch  on  the  gross  area  within  the  hooping,  the 
steel  stress  remaining  at  10,000  Ibs.  per  square  inch. 

12.  Longitudinal  bars  shall  be  securely  tied  together  at  intervals  not  exceeding  one  foot. 

13.  Hooping  or  ties  for  non-spiral  columns  shall  be  not  less  than  %  inch  in  diameter  for  all 
main  longitudinal  bars  of  one  inch  or  greater  in  diameter,  or  one-quarter  the  size  of  main  bars  for 
smaller  sizes. 

14.  Longitudinal  compression  rods  in  columns  shall  be  spliced  by  lapping  above  or  below 
the  floor  level  a  sufficient  amount  to  develop  the  stress  in  same  by  adhesion,  or  dowels  or  splice 
bars  shall  be  provided  sufficient  to  develop  not  less  than  three-quarters  the  calculated  stress  in 
the  bars  of  the  upper  column. 

PUNCHING  SHEAR 

15.  The  direct  or  punching  shearing  stress  on  concrete  shall  not  exceed  150  Ibs.  for  1-2-4 
(No.  6)  ;  130  Ibs.  for  1-2^-5  (No.  7^)  and  110  Ibs.  for  1-3-6  (No.  9)  and  shall  be  computed 
on  the  total  depth. 

NOTE:  Direct  or  punching  shear  results  from  the  action  of  a  column  on  its  footing,  or 
similar  construction,  and  is  not  to  be  used  as  a  measure  of  diagonal  tension. 

VERTICAL  SHEAR 

16.  The  unit  vertical  shearing  stress  in  beams  shall  be  used  as  a  measure  of  the  diagonal 
web  tension,  and  shall  not  exceed  150  Ibs.  per  square  inch  on  1-2-4  (No.  6)  concrete,  or  120  Ibs. 
on  1-2^-5  (No.  7^£)  concrete,  disregarding  the  reinforcement.    The  concrete  shall  be  assumed 
to  take  50  Ibs.  per  square  inch  for  1-2-4  (No.  6)  concrete   and  40   Ibs.   per   square   inch   for 
1-2^2-5  (No.  7^)  concrete.    Reinforcing  steel  shall  be  provided  for  the    balance.      The    unit 
vertical  shearing  stress  shall  be  determined  by  dividing  the  total  vertical  shear  by  the  effective 
shearing  area  [  =  beam  width  (b)  into  the  depth  between  the  lines  of  action  of  the  compressive 
and  tensile  stresses  (d3)].     The  unit  stress  in  the  concrete  shall  also  be  applied  to  the  effective 
shearing  area,  in  determining  the  total  vertical  shear  taken  by  the  concrete. 

ADHESION 

17.  The  adhesive  stress  of  concrete  to  plain  steel  bars  shall  not  exceed  60  Ibs.  per  square 
inch  for  1-2-4  (No.  6)  concrete,  nor  50  Ibs.  for  1-2^-5    (No.   7^)   concrete.     When  deformed 
bars  are  used,  these  values  may  be  doubled. 

ANCHORAGE 

18.  The  length  of  anchorage  required  to  develop  the  full  strength  of  plain  and  round  bars 
shall  be  determined  by  the  adhesion  as  given  above.     This  anchorage  may  be  reduced  50 %  for 
plain  bars  anchored  at  the  ends  by  bending  through  90°  or  more. 

13 


Watson's  Bridge   Specifications  Section  III 

TENSION 

19.  The  working  unit  stress  of  steel  reinforcing  bars  in  tension  shall  be  taken  at  16,000 
Ibs.  per  square  inch  for  structural  grade  and  18,000  Ibs.  for  hard  grade,  except  as  modified  herein 
for  steel  reinforcement  used  as  web  members. 

FOUNDATIONS 

20.  The  maximum  allowable  loads  on  foundations  shall,  unless  otherwise  indicated,  be  taken 
as  follows: 

On  dry  coarse  gravel,  well  cemented,  five  tons  (10,000  Ibs.)  per  sq.  ft. 

On  dry,  hard  sand  and  clay,  four  tons  (  8,000  Ibs.)  "       "     " 

On  ordinary  dry  clay  and  sand,  three  tons  (  6,000  Ibs.)  " 

On  wet  sand,  two  tons  (  4,000  Ibs.)  "       "     " 

On  wet  clay,  one  ton  (  2,000  Ibs.)  "      "     " 

The  maximum  allowable  load  on  foundation  material  other  than  that  given  will  be  determined 
for  each  individual  case  by  the  Engineer  in  charge. 

REINFORCED  STEEL 

21.  In  case  of  reinforced  steel  construction,  in  which  a  structural  steel  frame,  before  being 
encased  in  concrete,  is  designed  to  carry  a  definite  portion  of  the  loads,  the  unit  stresses  in  the 
steel  frame,  when  carrying  its  portion  of  the  load  alone,  must  not  exceed  those  allowed  by  the 
specifications  of  The  American  Railway  Engineering  Association,   and  the  unit  stresses  in  the 
steel  and  concrete  after  completion  shall  not  exceed  those  given  herein  for  reinforced  concrete 
construction. 


14 


Watson's  Bridge   Specifications  Section  IV 


Formulas 


In  computing  unit  stresses,  moments  of  resistances,  etc.,  the  following  formulas  shall  be  used. 

NOTATION 
The  units  are  always  in  pounds  and  inches  unless  otherwise  stated. 

dj  :=:  Total  depth  of  beam 

dg  =  Distance  from  compressive  surface  of  concrete  to  center  of  steel  reinforcement 

d3  =  jd2  =  Distance  from  centroid  of  compressive  forces  to  center  of  steel 

d'  =  Depth  from  compressive  surface  of  concrete  to  steel  in  compression 

j    =  Ratio  of  distance  between  centroid  of  compressive  forces  and  center  of  steel  to  dis- 
tance of  center  of  steel  below  compressive  surface  of  concrete 

k  —  Ratio  of  depth  of  neutral  axis  to  depth  of  steel  in  tension 
kd8  =  Distance  from  compressive  surface  to  neutral  axis  of  beam 

h   =  Ratio  of  depth  of  steel  in  compression  to  depth  of  steel  in  tension 

bj  =  Width  of  simple  or  width  of  stem  of  "T"  beam 

ba  —  Width  of  flange  of  "T"  beam 

t    =  Thickness  of  flange  of  "T"  beam 

O   —  Perimeter  of  a  reinforcing  bar  at  any  section 
.20    =:  Sum  of  perimeters  of  all  bars 

aj  =  Area  of  steel  tension  bars  at  any  cross-section 

a2  =  Area  of  web  reinforcing  bars  at  any  longitudinal  section  equal  to  d3  in  length 

a3  =  Area  of  steel  compression  bars  at  any  cross-section 

p    —  Ratio  of  cross-section  of  steel  in  tension  to  cross-section  of  beam  above  the  center  of 
gravity  of  the  steel  in  tension 

p'  —  Ratio  of  cross-section  of  steel  in  compression  to  cross-section  of  beam  above  the  center 
of  gravity  of  the  steel  in  tension 

s  =  Spacing  of  stirrups  at  any  section 
M   =  Bending  moment  in  inch  pounds  from  exterior  forces 

m   —  Moment  of  resistance  at  any  section  in  inch  pounds 

V   =  Vertical  shear  at  any  section 

f,  =  Unit  stress  in  steel  in  tension 

f ',  =  Unit  stress  in  steel  in  compression 

fc  =  Unit  stress  in  concrete  in  compression 

v    =  Unit  stress  in  concrete  in  shear 

u   =  Unit  stress  in  adhesion  of  concrete  to  steel 

E,  =  Modulus  of  elasticity  of  steel 

EC  —  Modulus  of  elasticity  of  concrete  in  compression 

Et  =  Modulus  of  elasticity  of  concrete  in  tension 

*=n 

EC 

A  =  Area  of  concrete  above  steel  in  case  of  beams,  also  total  area  of  columns 

Ac  =  Area  of  concrete  considered  as  taking  direct  compression  in  case  of  columns 

C  =  Total  compressive  stress  in  concrete 

S   —  Total  tensile  stress  in  steel 

S'  =  Total  compressive  stress  in  steel 

P  =  Total  safe  load  on  columns 

15 


Watson's  Bridge   Specifications 


Section  IV 


1.    RECTANGULAR  BEAMS 


r 


ti 


-*s 


Position  of  neutral  axis, 


k  =  V  2  pn  +  (pn)3  —  pn 
Arm  of  resisting  couple, 


(For  fs  =  15,000  to  16,000,  and  fc  =  600  to  650,  k  may  be  taken  at  f  .) 
Fiber  stresses, 


fs  = 


M 


M 


LI  jd2       PJbi 
f  2M        2  pfs 

jkbdj  k 


Steel  ratio, 


1 


P=  ~ 


H-t+O 

fc  vnfc        / 


a,  = 


2    f s  /  f s 

i 

M 
d8fs 


(1) 

(2) 

(3) 
(4) 

(5) 
(6) 


16 


Watson's  Bridge   Specifications 


Section  IV 


2.    "T"  BEAMS 


J 


r~ 
t 

*__ 


t± 


*<* 


«^— 
C 


X 


X 


X 


•#-/? 


Case  I.    When  the  neutral  axis  lies  in  th«  flange  (use  the  formulas  for  rectangular  beams). 

Case  II.     When  the  neutral  axis  lies  in  the  stem. 

The  following  formulas  neglect  the  compression  in  the  stem  : 

Position  of  neutral  axis, 


2n  al    +  2b2  t 

Position  of  resultant  compression, 
3kd2  —  2t  t 


2kd2  —  t    3 

ig  couple, 

=  do  —  z 

(9) 

M 

(10) 

ai  jd2 

Mkd                   fs    k 

fill 

Fiber  stresses, 


fc  = 

b2  t  (kd2  —  |  t)  jd2        n   1  —  k 

(For  approximate  results,  the  formulas  for  rectangular  beams  may  be  used.) 

The  following  formulas  take  into  account  the  compression  in  the  stem;  they  are  recom- 
mended where  the  flange  is  small  compared  with  the  stem  : 


17 


Watson's  Bridge   Specifications 

Position  of  neutral  axis, 


Section  IV 


kd  2nd2 


(b2-b1)  t2 


(b2  -  bt)  t 


nat  4-  (b2  —  bj  t 

Position  of  resultant  compression, 

(kd2  t2--  1 
z=  V      2  3 


[( 


kd 


t  (2kd2  -t)  b2  4-  (kda-  t)2  b, 
Arm  of  resisting  couple, 

Fiber  stresses, 

fs  = 

((2kd2  -  t)  b2  t-  (kd2  -  t)2  bx)  jd. 
3.     BEAMS  REINFORCED  FOR  COMPRESSION 


Position  of  neutral  axis, 
k 


=  J2n(p  +  p'-     +  n*  (p  4-  p')2  -  n  (p  +  p') 
v  d  2 


Position  of  resultant  compression, 


z  = 


(12) 


(13) 


I 

M 

(15) 

ai  jd2 
2Mkd2 

(16) 

(17) 


(18) 


18 


Watson's  Bridge   Specifications  Section  IV 

Arm  of  resisting  couple, 

jd2=da-z (19) 

Fiber  stresses, 

fc=-  -^ r. •     (20) 


- 
f's  =  nfc    *       d         ................     (22) 


4.  SHEAR,  BOND  AND  WEB  REINFORCEMENT 

In  the  following  formulas,  2O  refers  only  to  the  bars  constituting  the  tension  reinforcement 
at  the  section  in  question,  and  jd2  is  the  lever  arm  of  the  resisting  couple  at  the  section. 


For  rectangular  beams. 


bjd2 
u  = 


V  (23) 


V  (24) 


jd2  20 
(For  approximate  results,  j  may  be  taken  at  £.) 

The  stresses  in  web  reinforcement  may  be  estimated  by  the  following  formulas : 

Vertical  web  reinforcement, 

S'  =  ^- (25) 

Web  reinforcement  inclined  at  45°. 

S'=0.7-Yl (26) 

Jd2 

in  which  S'  =  stress  in  single  reinforcing  member,  V  =  amount  of  total  shear  assumed  as  carried 
by  the  reinforcement,  and  s  =  horizontal  spacing  of  the  reinforcing  members. 

The  same  formulas  apply  to  beams  reinforced  for  compression  as  regards  shear  and  bond 
stress  for  tensile  steel. 

For  "T"  beams, 


u=t    v (28) 

(For  approximate  results,  j  may  be  taken  as  £ .) 


19 


Watson's   Bridge   Specifications  Section  IV 


5.     GENERAL 

The  length  of  reinforcing  bars  required  in  a  simple  beam  uniformly  loaded  may  be  deter- 
mined as  follows : 


/at  +  a2  +     .  an   >  (29) 

Xn  —  Lt+J  ^ 

where  xn  —  length  of  nth  rod  in  tlie  order  of  length,  counting  the  shortest  as  number  one : 
L  =  span  length. 
A  =  total  area  of  steel  at  center ;  and  alf  a2,  etc.,  =  area  of  each  rod  up  to  the  nth  rod. 

For  unsymmetrical  loading  the  maximum  moments  and  shears  must  be  determined  at  various 
sections  and  the  lengths  of  bars  obtained  therefrom  preferably  by  plotting  the  moment  and  shear 
diagrams. 

6.    APPROXIMATE  METHOD  FOR  DESIGNING  "T"  BEAMS 

By  the  use  of  the  "Table  for  Designing  "T"  Beams,"  "T"  beams  may  be  designed  in  exactly 
the  same  manner  as  simple  rectangular  beams,  by  considering  the  width  b2  of  the  "T"  beam  to 
correspond  to  the  width  bl  of  the  rectangular  beam,  and  the  area  of  concrete  above  the  steel  to  be 
equal  to  d2  b2. 

When  the  thickness  t  of  the  flange  is  less  than  the  distance  from  the  compressive  surface  of 
the  slab  to  the  neutral  axis,  the  unit  stresses  on  concrete  in  compression  are  increased,  and  there- 
fore in  designing  such  "T"  beams  as  if  they  were  simple  rectangular  beams,  a  corresponding 
reduction  in  the  percentage  of  reinforcement  must  be  made,  in  order  to  keep  the  ratio  fs  -*-  fc 
constant. 

The  following  table  gives  the  allowable  percentage  of  steel  in  terms  of  the  ratio  of  the  thick- 
ness of  the  flange  to  the  depth  d2. 


Watson's   Bridge    Specifications 


Section  IV 


TABLE  SHOW/NO  THE  ALLOWABLE  PERCENTAGE  OF  STEEL 

VARIOUS  VALUES  OF  "fs  &  "fif.  IN  TERMS  OF  THE   RATIO   OF   THE 
THICKNESS  OF  THE  FLANGE  "t"     TO  THE   DEPTH  "da". 


2* 

«•'• 

QC4i 

fs   =  |600Oy°' 

fs  =  18000*/0' 

t?~ 

!£« 

fc=600 

£>650 

&=700 

J&--750 

£•600 

fc-65O 

fe»700 

fc-rso 

.10* 

.32 

.35 

.39 

.42 

.26 

.3; 

.35 

.38 

JO 

.15 

.46 

.60 

.54 

.58 

.39 

.43 

40 

.52 

.IS 

20 

.55 

60 

.66 

72 

.47 

.52 

50 

.63 

.20 

25 

.61 

.68 

.75 

.63 

.52 

.58 

.65 

.72 

25 

30 

.66 

.74 

52 

30 

.56 

.62 

to 

.76 

.30 

.35 

.67 

.76 

.85 

34 

56 

.63 

.71 

.QO 

.35 

.40 

.67 

.77 

.87 

.97 

56 

.63 

.72 

•81 

40 

THIS  TABLE:  FOP  USE  IN  THE  DESIGN  OF  "r"  BEAMS 
COMPRESSION  /N  THE  WEB  is  NEGLECTED. 


U      : 
(/>  -J 

</>  UJ 


° 


CM 


cvi 


S 


to 


a 


M 


01 


8 

0) 


CO 


m 


00 


to 


CO 


i 


8 


O 


vo 


s 


s 


§ 


§ 


% 


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«o 


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vfi 


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21 


Watson's   Bridge    Specifications  Section  V 


Quality  of  Materials  for  Concrete  Work 


PORTLAND  CEMENT 

1.  All  cement  shall  be,  unless  otherwise  specified,  American   Portland   Cement  of   a  well 
known  and  tried  brand.    Unless  otherwise  specified,  all  cement  shall  be  purchased  subject  to  the 
standard  tests  of  the  American  Society  for  Testing  Materials,  and  these  tests  shall  be  made  in 
strict  accordance  with   the  methods   prescribed  by  the   Committee  on   Uniform   Tests   of   the 
American  Society  of  Civil  Engineers.    Tests  shall  be  made  from  at  least  each  carload  of  cement 
and  no  cement  shall  be  used  on  the  job  until  such  tests  shall  have  been  made.     Cement  must  be 
ordered  sufficiently  in  advance  of  its  use  to  allow  at  least  7  days  for  testing. 

2.  The  requirements  for  Portland  Cement  are,  briefly,  as  follows : 

The  specified  gravity,  thoroughly  dried  at  110°  Centigrade,  shall  be  not  less  than  3.10. 

For  fineness,  it  shall  leave  by  weight  a  residue  of  not  more  than  S%  on  the  No.  100  and  not 
more  than  25  %  on  the  No.  200  sieve. 

For  time  of  setting,  it  shall  develop  the  initial  set  in  not  less  than  30  minutes,  but  must 
develop  the  hard  set  in  not  less  than  1  hour  or  more  than  10  hours. 

The  minimum  requirements  for  tensile  strength  of  neat  cement  shall  be  as  follows : 

Age — 24  hours  in  moist  air 175  Ibs. 

Age —  7  days  (1  day  in  moist  air,     6  days  in  water) 500  Ibs. 

Age — 28  days  (1  day  in  moist  air,  27  days  in  water) 600  Ibs. 

For  tensile  strength  of  briquettes  composed  of  one  part  cement  to  three  parts  sand,  as  herein 
specified,  the  minimum  requirements  shall  be  as  follows : 

Age —  7  days  (1  day  in  moist  air,     6  days  in  water) 175  Ibs. 

Age — 28  days  (1  day  in  moist  air,  27  days  in  water) 200  Ibs. 

(Using  Standard  Ottawa  sand,  the  above  minimum  requirements  shall  be  .200  Ibs.  and  275  Ibs. 
per  square  inch.) 

For  constancy  of  volume  three  pats  of  neat  cement  about  3  inches  in  diameter  and  about 
l/2  inch  at  the  center  and  tapering  to  a  thin  edge  shall  be  made,  one  of  which  shall  be  kept  in  moist 
air  for  a  period  of  24  hours  and  then  in  air  at  normal  temperature  for  28  days.  Another  shall  be 
kept  in  moist  air  for  24  hours  and  then  kept  in  water  maintained  as  near  70°  Fahr.  as  practicable 
for  28  days.  The  third  shall  be  kept  24  hours  in  moist  air  and  then  exposed  in  an  atmosphere 
of  steam  above  boiling  water  in  a  loosely  closed  vessel  for  5  hours.  These  pats  shall  remain  firm 
and  hard  under  the  above  tests  and  shall  show  no  signs  of  distortion,  checking,  cracking  or  dis- 
integration. 

Portland  Cement  shall  contain  not  more  than  1.75%  of  anhydrous  sulphuric  acid  nor  more 
than  4%  of  magnesia.  (Mgo.) 

3.  True  Portland  Cement  made  from  blast  furnace  slag  will  be  classed  with  other  Portland 
Cements. 

POZZULAN  CEMENT 

4.  Pozzulan  Cement,  if  used,  will  be  understood  to  mean  cement  made  directly  from  blast 
furnace   slag  and  lime  without  calcination  subsequent  to  the  mixing.     It  shall  be  used  only 
under  water  or  other  places  where  thoroughly  protected  from  the  atmosphere.    It  shall  weigh  not 
less  than  330  Ibs.  per  barrel  and  it  shall  meet  the  fineness,  soundness    and    setting    tests    as 
prescribed  for  true  Portland  Cement  and  shall  have  a  specific  gravity  of  not  less  than  2.7  and 
shall  develop  a  tensile  strength  not  less  than  75%  of  that  specified  for  Portland  Cement. 

22 


Watson's   Bridge   Specifications  Section  V 

CONCRETE  AGGREGATE 

5.  Concrete  will  be  composed  of  cement  and  aggregate,  the  latter  being  separated  into  fine 
aggregate,  consisting  of  material  less  than  %  mch  in  size,  and  coarse  aggregate,  consisting  of 
material  over  ^  mcn  m  size-    Unless  otherwise  specified,  fine  aggregate  shall  be  composed  of 
sand,  and  coarse  aggregate  of  crushed  stone,  slag  or  screened  gravel,  as  hereinafter  described. 

SAND 

6.  Sand  shall  consist  of  grains  of  hard,  tough,  durable  rocks.    For  first  grade  sand,  not  more 
than  4%  and  for  second  grade  sand,  not  more  than  8%,  by  weight,  of  soft,  decayed  or  friable 
material,  shall  be  allowed.     First  grade  sand  shall  contain  not  more  than  2%  and  second  grade 
sand  not  more  than  4%,  by  weight,  of  finely  divided  clay,  loam  or  other  suspended  materials, 
when  tested  by  washing  in  such  a  manner  as  to  remove  all  such  material  without  removing  any  of 
the  fine  sand ;  provided  that  if  the  tensile  strength  of  the  mortar  made  from  such  sand,  as  herein- 
after provided  for,  be  greater  than  110%  of  the  strength  of  similar  mortar  made  from  standard 
Ottawa  sand,  the  allowable  amount  of  suspended  material  may  be  increased  to  3%  for  first  grade 
sand.    This  suspended  matter  must  not  form  a  coating  around  the  grains  that  cannot  be  entirely 
removed  by  wetting  and  agitating,  such  as  takes  place  in  the  ordinary  process  of  mixing.    Sand 
shall  be  free  from  oily  or  greasy  matter  in  any  form   and   shall   not   contain   organic  matter   in 
excess  of  10%  of  the  amount  of  suspended  matter  when  tested  as  above  described. 

7.  The  grains  shall  be  well  graded  in  size  from  the  finest  to  the  coarsest.     Not  more  than 
10%'  for  first  grade  sand  and  15%  for  second  grade,  by  weight,  including  the  suspended  matter, 
shall  pass  the  No.  100  sieve  and  not  more  than  15%   for  first  grade  sand  and  85 %   for  second 
grade,  shall  pass  the  No.  16  sieve. 

8.  The  voids  in  the  dry  sand,  when  well  shaken,  shall  not  exceed  35%>  for  first  grade  sand, 
nor  4:0%  for  second  grade  sand.    The  method  of  determining  the  voids  shall  be  as  follows: 

A  container  holding  not  less  than  .12  cu.  ft.  (in  shape  either  a  cube  or  a  cylinder,  having  a 
height  approximately  equal  to  its  diameter)  is  filled  in  1  inch  layers,  dropping  twice  a  distance  of 
2  inches  after  placing  each  layer.  Sand  is  then  weighed  carefully  and  the  percentage  of  voids 
determined  by  computation,  assuming  the  specific  gravity  of  sand  to  be  2.60. 

9.  Mortar  briquettes  mixed  in  the  proportion  of  1  to  3  by  weight  and  tested  in  accordance 
with  the  requirements  of  the  standard  specifications  for  testing  cement,  shall  develop  a  tensile 
strength  of  at  least  70%  of  the  strength  of  similar  briquettes  made  of  the  same  cement  and  stand- 
ard Ottawa  sand. 

10.  Unless  otherwise  specified,  first  grade  aggregate  shall  be  used  for  all  reinforced  concrete 
work,  for  all  mixtures  of  1-2-4  (No.  6)  or  richer.     Second  grade  aggregate  may  be  used  for  large 
masses  of  concrete  of  1-2^-5  (No.  7  ^2)  mix  or  poorer. 

11.  Stone  screenings  shall  not  be  used  for  fine  aggregate,  except  by  express  permission  of 
the  Engineer  in  charge,   who  will  determine  the  amount  of  sand  to  be  added  to  the  screen- 
ings for  each  particular  case,  or,  if  found  necessary   to    screen   the   material,   he   will   decide 
what  part  of  the  material  shall  be  screened  out. 

STONE 

12.  Stone  for  massive  concrete  work  shall  be   crushed,  hard  limestone,  granite,   trap,  or 
other  suitable  hard,  clean  stone  in  graded  sizes  of  from  ^4  mcn  to  3  inches  where  it  is  practical 
to  use  sizes  as  large  as  this.    Stone  for  reinforced  concrete  work  shall  be  of  similar  material,  but 
of  smaller  size.    For  ordinary  work,  sizes  shall  be  from  %  to  1  inch.    For  small  reinforced  con- 
crete sections  the  maximum  size  shall  not  exceed  %  inch.    All  stone  shall  have  a  cubical  fracture 
and  shall  be  of  material    that    is    not    subject  to  disintegration,  due  to  atmospheric  or  other 
influences  to  which  the  concrete  will  be  subject. 

23 


Watson's  Bridge    Specifications  Section  V 

GRAVEL 

13.  Gravel  for  concrete  work  shall  be  clean  graded  gravel  in  sizes  specified  for  stone.  For 
first  grade  gravel,  not  more  than  4%  and  for  second  grade  gravel,  not  more  than   8%,  by 
weight,  of  soft,  decayed  or  friable  material  will  be  allowed.    When  gravel  is  not  well  graded  or 
not  uniform,  the  Engineer  may  determine  the  proportions  for  each  grade  brought  upon  the  work, 
so  as  to  give  results  equivalent  to  those  of  the  specified  mix. 

SLAG 

14.  Slag  for  concrete  work  shall  be  air  cooled  crushed  slag  in  sizes  similar  to  those  specified 
for  crushed  stone.    First  grade  slag  shall  contain  not  more  than  1.75%  of  sulphur  or  48%  of  lime 
and  not  less  than  33%  of  silica  and  shall  weigh  not  less  than  75  Ibs.  per  cubic  foot.    Second  grade 
slag  shall  contain  not  more  than  2%  of  sulphur  or  50%  of  lime  and  not  less  than  30%  of  silica 
and  shall  weigh  not  less  than  65  Ibs.  per  cubic  foot.     In  testing  slag  for  weight,  all  materials 
over  \y*  inch  and  under  %  inch  in  size  shall  be  screened  out;  the    material    thoroughly    dried; 
placed  in  a  container  holding  not  less  than  1  cubic   foot,   in   shape  either  a  cube  or  a  cylinder 
(having  a  height  approximately  equal  to  its  diameter)  ;  filled  in  four  layers ;  and  compacted  by 
dropping  twice  a  distance  of  2  inches  after  placing  each  layer. 

SCREENINGS  AND  SCREENS 

15.  All  stone,  gravel  or  slag  shall  be  screened,  unless  otherwise  distinctly  arranged  with  the 
Engineer  and  shall  be  subject  to  the  Engineer's  acceptance.     Crusher  dust  in  excess  of  5%,  by 
weight,  shall  be  cause,  for  rejection.    All  material  passing  a  No..  100  sieve  shall  be  considered  to 
be  dust.     In  testing^  materials,  for  size,  sieves  with  round  holes  shall  be  standard. 

CINDERS 

16.  First  grade  cinders,  when  used  for  concrete  supporting  work,  shall  be  hard,  well  burned 
vitreous  clinkers,  free  from  soft  powdered  ash  and  containing  not  more  than  10%  of  unburned 
coal.     The  crushing  strength  of  standard  cylinders  of  cinder  concrete,  mixed  in  the  proportions 
of  1-2-4  (No.  6)  shall  be  not  less  than  800  Ibs.  per  square  inch  at  28  days.    Material  not  meeting 
these  requirements  shall  not  be  used  for  reinforced  concrete.     The  sulphur  contents   shall  not 
exceed  1%.    Second  grade  cinders,  which  may  be  used  for  filling  concrete  subfloors  or  other  non- 
supporting  parts,  may  have  20%  unburned  coal  and  2%   sulphur,  and  will  not  be  required  to 
meet  the  compressive  strength  as  given  above. 


17.  Water  used  in  concrete  mixing  shall  be  reasonably  clear  and  free  from  oil,  acids  and 
injurious  amounts  of  alkalies  or  vegetable  matter.     Roily  or  brackish  water  shall  not  be  used.    Sea 
water  will  not  be  allowed. 

STEEL 

18.  Steel  shall  be  manufactured  in  accordance   with   the   Standard    Specifications   of   the 
American  Society  for  Testing  Materials,  as  adopted  June  1,  1912,  and  shall  be  purchased  subject 
to  the  tests  therein  described.     (Carnegie  Hand-Book,  16th  Edition,  page  32). 

19.  The  quality  and  shape  of  reinforcing  steel  to  be  used  must  be  as  shown  on  the  drawings. 

20.  Chain  or  cable  reinforcing  shall  not  be  used  unless  it  is  of  a  type  that  shall  have  been 
shown  by  tests,  satisfactory  to  the  Engineer,  not  to  stretch  more  than  plain  bars  of  same  net  cross 
section  under  the  same  load. 

21.  Steel  for  reinforcing  concrete  shall  not  be  painted  and  shall  be  free  from  grease,  dirt 
and  deep  rust  when  placed  in  the  work. 

INSPECTION 

22.  When  an  inspector  is  furnished  by  the  purchaser  to  inspect  material  at  the  mills,  he 
shall  have  full  access,  at  all  times,  to  all  parts  of  mills  where  material  to  be  inspected  by  him  is 
being  manufactured. 

24 


Watson's  Bridge   Specifications  Section  VI 


Proportioning,  Mixing  and  Placing  Concrete 


1.  All  concrete  proportions  specified  herein  will  be  based  upon  the   assumption   that  one 
barrel  of  Portland  Cement  is  equivalent  to  3.8  cu.    ft.   and  all  proportioning  must  be  done  by 
means  of  a  carefully  gauged  wheelbarrow  or  other  apparatus  which  will  be  determined  by  the 
Engineer. 

PROPORTIONS  AND  STRENGTH 

2.  The  quantities  of  materials  required  for  one  cubic  yard  by  specified  proportions  and  the 
required   minimum   compressive    strength    at    60  days  shall  be  as   follows,  all  volumes  being 
measured  loose : 

<3trmo   <?lo»  m-          Compressive 

Mix  No.  Proportion  Cement  in  barrels.     Sand  cu.  yds.        p~*     ,'  D  ag  °,r  Strength 

rei,  cu.  yas.         &t  6Q  d&ys 

4y2  1-1^-3  2.00  0.42  0.84  2400 

5  1-2-3  1.81  0.51  0.76  2200 

6  1-2-4  1.57  0.44  0.88  2000 
7V2  1-2^-5  1.30  0.46  0.92  1800 
9  1-3-6  1.11  0.47  0.94  1600 

Iiy2       1-  3  -6  x  %  rubble  0.83  0.35  0.71  1600 

10y2       l-3>£-7  0.96  0.48  0.96  1400 

13  1-3^-7  x  %  rubble  0.72  0.36  0.72  1400 

UNIT  STRESSES 

3.  The  unit  stresses  given  in  Section  III  and  formulas  given  in  Section  IV  apply  to  con- 
crete which  shall  show  strengths  equal  to  those  herein  given  for  stone,  slag  or  gravel  concrete. 
For  mixtures  which  show  a  less  strength  the  unit  stresses  shall  be  correspondingly  reduced.    The 
values  used  for  designing  shall  be  the  strength  at  60  days,  the  samples  being  stored  in  water. 

COMPRESSIVE  STRENGTH 

4.  In  determining  the  compressive  strength  of  mortars,  the  latter  may  be  assumed  at  nine 
times  the  tensile  strength  of  standard  briquettes  having  the  same  proportion  of  cement  to  sand  as 
used  in  the  concrete. 

5.  The  compressive  strength  of  concretes  shall  be  determined  from  a  standard  test  piece 
8  inches  in  diameter  and  16  inches  in  length  (or  6x6x6   inch   cubes,  as   directed),  using  same 
materials  and  same  mixture  as  specified,  storing  in  air  for  two  days  and  in  water  for  the  balance. 
Such  samples  shall  show  a  strength  at  least  equal  to  that  specified  above  at  60  days,  or  75  %  of 
such  strength  at  30  days. 

MIXING 

6.  All  mixing  shall  be  by  machinery,  except  such  hand  mixing  as  may  be  allowed  by  special 
arrangement  with  the  Engineer. 

7.  If  concrete  is  mixed  by  hand,  the  sand  and  cement  shall  be  spread  upon  the  mixing 
board  in  thin  layers  and  turned  with  spades  until  the  mixture  is  of  uniform  color.     Stone  and 
water  shall  then  be  added  and  the  mix  turned  at  least  three  times,  not  counting  the  shoveling  off 
the  board. 

25 


Watson's   Bridge    Specifications  Section  VI 

8.  Preference  will  be  given  to  revolving  batch  machines  which  automatically  measure  the 
ingredients  of  the  mix.  Mixing  must  be  very  carefully  and  thoroughly  done.  Sufficient  water 
shall  be  used  to  make  the  mass  plastic  enough  to  run  freely.  Excess  of  water  over  this  shall  not 
be  used. 

9-  For  massive  concrete  work,  only  enough  water  shall  be  used  to  make  the  concrete  plastic, 
not  so  wet  but  that  it  may  be  churned  with  a  light  tamper  to  quake  the  mass. 

10.  The  concrete  shall  be  placed  in  position  immediately  after  mixing  and  before  the  initial 
set  shall  have  taken  place. 

TAMPING 

11.  All  concrete  work  shall  be  tamped  wherever,  in  the  opinion  of  the  Engineer  in  charge, 
tamping  is   required   to   properly   compact   the  mass.       In     tamping    concrete     for     reinforced 
work,  special  tools  shall  be  provided  for  working  around   and   under   reinforcing  bars,   tamping 
against  forms,  etc. 

RETEMPERING 

12.  No  retempering  of  concrete  which  has  been  allowed  to  stand  until  the  initial  set  has 
taken  place  will  be  allowed  unless  by  special  permission  of  the  Engineer,  who  may,  at  his  dis- 
cretion, require  additional   cement  to  be  used  in  retempering. 

JOINTS 

13.  The  mixing  and  placing  of  concrete  shall  be,  as  far  as  practicable,  a  continuous  opera- 
tion, and  when  it  is  necessary  to  make  a  joint  in  monolithic  concrete,  it  shall  preferably  be  made 
in  the  middle  of  a  panel  at  right  angles  to  the  beams  and  by  means  of  a  stop  board  placed  in  a 
vertical  position  and  containing  a  key  on  the  side  next  the  concrete  first  placed.    When  these  stop 
boards  are  removed,  the  exposed  surfaces  of  concrete  shall  be  wet  and  carefully  dusted  with  neat 
cement  or  painted  with  mortar  before  continuing  the  next  block. 

BONDING 

14.  When  it  is  necessary  to  bond  new  concrete  to  concrete    partially    or    wholly    set,    the 
Engineer    may    require    that    the    surfaces    of  the    old    concrete    be    roughened     either    by 
picking  or  by  washing  with  acid,  thoroughly  rinsing  same  off  and  applying  a  thin  coat  of  rich 
cement    mortar,    1  to  1,    or    a    bonding    preparation    may    be    used    by    permission    of    the 
Engineer.    It  will  always  be  required  in  joining  new  concrete  to  old  that  has  partially  set,  that 
part  of  the  old  concrete  next  to  the  forms  on  exposed  surfaces  shall  be  removed  for  a  depth  of 
at  least  one  inch  and  a  distance  back  from  the  face  of  the  concrete  of  at  least  two  inches,  in 
order  to  avoid  the  appearance  of  a  joint.     It  will  also  be  necessary  to  remove  all  laitance  from 
the  surface  of  concrete  which  has  partially  set  before  attempting  to  bond  new  concrete  thereto. 
When  practicable,  large  angular  stones  shall  be  embedded  in  horizontal  joints  of  massive  concrete 
work,  to  assist  in  bonding  the  old  concrete  to  the  new. 

WETTING 

15.  Concrete  shall  be  kept  wet  for  one  week  after  depositing  and  in  dry  hot  weather  shall, 
in  addition,  be  kept  covered  from  exposure  to  the  sun  during  this  time,  or  shall  be  constantly 
sprinkled  during  the  day  by  a  workman  especially  detailed  for  this  work. 

26 


Watson's   Bridge    Specifications  Section  VI 

PLACING  UNDER  WATER 

16.  When  it  is  necessary  to  place  concrete  under  water,  the  site  shall  be  inclosed  with  a 
cofferdam  or  other  means  taken  to  procure  quiet  water  and  then  the  material  shall  preferably  be 
deposited  from  a  bucket  provided  with  a  bottom  dump,  or  a  tremie  may  be  used.    Care  must  be 
taken  to  keep  the  surface  of  the  concrete  as  nearly  horizontal  as  possible  when  depositing  under 
water.    When  concrete  is  deposited  under  water,  the  deposition  shall  be  continuous,  or  else  means 
shall  be  provided  to  remove  the  laitance  from  the  top  of  concrete  previously  deposited  before 
resuming  the  pouring. 

17.  When  concrete  must  be  deposited  in  running  water,  it  shall  be  done  by  placing  the 
concrete  in  bags  and  depositing  the  bags  in  place,  or  by  other  means  equally  satisfactory  to  the 
Engineer. 

18.  Unit  stresses  on  concrete  deposited  as  per  paragraph  No.  16  must  be  decreased  33%%, 
and  when  deposited  as  per  paragraph  No.  17,  50%. 

RUBBLE  CONCRETE 

19.  In  heavy  foundation  work  or  other  work  requiring  large  masses  of  concrete,  the  Con- 
tractor may  use  not  to  exceed  50%  of  stones  to  embed  in  the  concrete  when  so  indicated  on  the 
drawings.     Such  stones  must  be  sound,  clean  and  wet  before  placing,  and  shall  not  be  placed 
nearer  than  six  inches  from  the  surface  of  the  concrete  and  not  less  than  six  inches  apart.    They 
must  be  laid  with  their  largest  face  at  right  angles  to  the  line  of  principal  stress. 

DROPPING 

20.  In  placing  concrete  it  shall  not  be  dropped  from  a  greater  height  than  10  feet.     When 
it  is  required  to  place  concrete  from  a  greater  height  than  10  feet,  it  shall  be  placed  by  means  of 
chutes  or  other  devices  satisfactory  to  the  Engineer  in  charge. 

CHUTES 

21.  When  concrete  is  deposited  by  inclined  chutes,  the  slope  shall  be  adjusted  so  that  there 
will  be  no  separation  of  ingredients  in  transit.     The  Engineer  in  charge  may  require  remixing, 
whenever,  in  his  judgment,  there  is  such  separation  of  ingredients. 

APPROVAL  OF  METHOD  OF  MIXING  AND  PLACING 

22.  The  method  of  mixing  and  placing  shall  be  submitted  to  the  Engineer  in  charge  before 
beginning  work  and  shall  be  subject  to  his  approval. 

SAMPLE  BLOCKS 

23.  Whenever  requested,  by  the  Engineer,  the  Contractor  shall  pour  sample  blocks,  eight 
inches  in  diameter  and  16  inches  high,  or  six  inch  cubes,  as  directed,  which  shall  be  properly 
marked  for  identification  and  stored  as  directed  by  the  Engineer. 

GENERAL 

24.  If   materials   other   than    screened   broken  stone,  slag  or  gravel  and  sand,  as  herein 
described,  be  used,  the  proportions  shall  be  subject  to  such  changes  as  shall  be  found  to  give 
equivalent  results  in  strength  and  density  to  the  results  obtained  by  use  of  the  specified  proportions 
and  materials. 

27 


Watson's   Bridge    Specifications  Section  VI 

25.  It  is  understood  that  these  proportions  and  all  other  proportions  given  in  these  specifi- 
cations are  subject  to  such  changes  as  may  be  found  necessary  in  order  to    obtain    properly 
proportioned  mixtures  after  the  Engineer  shall  have  had  made  careful  analyses  of  the  materials 
proposed  to  be  used. 

26.  In  case  such  adjustment  of  the  proportions  entails  a  larger  proportion  of  cement  to 
aggregates  than  that  specified,  the  Contractor  will  be  allowed  the  actual  cost,  delivered  at  the 
mixer,  of  such  additional  cement,  the  amount  to  be  determined  by  using  the  amount  as  given  in 
the  preceding  table  as  a  basis.    In  case  a  less  amount  of  cement  be  required,    a    corresponding 
amount  shall  be  deducted  from  the  contract  price. 

27.  In  any  mixture,  the  matrix  (cement  and  sand  mortar)   shall  exceed  the  voids  in  the 
aggregate  (broken  stone,  gravel,  etc.). 

28.  Reinforced  concrete  footings  shall  be  poured  in  one  continuous  operation,  unless  other- 
wise indicated  on  the  plans. 

29.  "T"  beams  must  have  the  stem  and  slab  poured,  in  one  continuous  operation,  except  in 
the  case  of  constructions  especially  designed  to  secure  a  positive  bond  between  the  several  parts. 

30.  Spandrel  beams  projecting  above  the  slab  shall  be  poured  at  the  same  time  as  the  slab 
unless  otherwise  specified  or  shown  on  the  drawings. 

31.  Sufficient  time  shall  be  allowed  after  pouring  columns  and  walls  and  before  pouring  the 
beams  and  slabs  at  top  of  same,  to  allow  for  shrinkage  of  columns  or  walls. 


28 


Watson's   Bridge    Specifications  Section    VII 


Requirements  for  Placing  Reinforcing  Steel,  Inserts,  Etc. 


1.  Steel  reinforcement  shall  be  secured  against  displacement  during  the  pouring  of  the  con- 
crete, by  mechanical  spacers  and  chairs,  or  other  positive  means,  and  shall  be  subject  to  a  rigid 
inspection  by  and  approval  of  the  Engineer  in  charge  immediately  prior  to  placing  concrete. 

CLEARANCE 

2.  The  clear  distance  from  the  surfaces  of  the  concrete  to  the  steel  shall  be,  unless  other- 
wise shown,  2~y2  inches  for  footings,  arches,  retaining  walls,  etc.,  2  inches  for  columns,  1^  inches 
for  girders  and  beams,  1  inch  for  slabs  8  inches  and  more  in  thickness,  and  Y^  inch  for  slabs  under 
8  inches  thick. 

3.  Main  bars  in  slabs  shall  be  spaced  a  distance  apart  not  to  exceed  one  and  one-half  times 
the  thickness  of  the  slab,  and  cross  bars  shall  always  be  used  at  right  angles  to  the  main  carrying 
bars.    Cross  bars  shall  not  be  less  than  %  inch  diameter  and  spaced  a  distance  apart  not  to  exceed 
twice  the  specified  maximum  distance  for  main  carrying  bars.    These  limits  do  not  apply  to  wire 
mesh  or  other  fabricated  reinforcement. 

4.  The  clear  distance  between  reinforcing  bars  shall  never  be  less  than  twice  the  maximum 
diameter  of  stone  or  bar  used. 

COLUMN  BARS 

5.  In  the  case  of  columns  containing  longitudinal  reinforcing  bars,  positive  means  shall  be 
provided  for  splicing  such  bars.     At  the  base  of  the  column,  proper  provision  must  be  made  for 
transmitting  the  load  carried  by  the  reinforcing  bars  to  footings.     Unless  otherwise  shown  on 
the  drawings,  this  shall  be  done  by  means  of  anchor  dowels.    Column  bar  splices  shall  be  made 
at  the  floor  level  by  means  of  dowels,  unless  otherwise  shown  on  the  drawings. 

6.  Column  bars  1  inch  in  diameter  and  over  shall  be  tied  together  by  horizontal  hoops  not 
less  than  %  inch  diameter  and  not  farther  apart  than  12  inches.     The  distance  between  spirals 
shall  not  exceed  3  inches.    For  column  bars  less  than  1  inch  diameter,  the  size  of  the  tie  bars  may 
be  one-fourth  of  the  diameter  of  the  column  bars. 

7.  Spirals,  hoops  and  tie  bars  shall  be  secured  to  vertical  bars    at    intervals    of    not    over 
12  inches  and  all  spirals  shall  be  provided  with  satisfactory  spacers. 

ANCHOR  BOLTS,  ETC. 

8.  Wherever  bolts  are  to  be  embedded  in  the  concrete,  these  bolts  shall  be  placed  in  position 
by  the  Contractor  for  concrete  work,  unless  otherwise  specified. 

9.  The  Contractor  for  concrete  work  shall  place  all  anchor  bolts  for  columns,  beams,  etc., 
and  shall  place  all  anchors  and  ties  for  all  attachments  to  the  concrete  work,  such  as  terra  cotta 
or  cast  concrete  trimmings  and  facings,  brick  facings,  etc. 

10.  Wherever  pipes,  wires,  conduits,  or  other  fixtures  not  otherwise  provided  for  herein, 
are  to  be  encased  in  the  concrete  work,  they  shall  be  furnished  and  placed  under  separate  con- 
tract, unless  otherwise  provided  for  on  the  plans  or  in  the  contract.    This  Contractor  shall  not 
pour  the  concrete  without  notifying  the  other  trades  sufficiently  in  advance  to  allow  them  to  place 
their  work. 

29 


Watson's  Bridge   Specifications  Section    VII 

GENERAL 

11.  All  steel  for  reinforcing  shall  be  placed  with  great  care;  all   abrupt  bends  must  be 
avoided,  except  where  one  steel  member  is  bent  around  another. 

12.  Bending  shall  be  done  cold  unless  otherwise  ordered.    If  bars  are  heated  and  blacksmith 
work  done,  care  must  be  exercised  that  the  steel  is  not  burned  in  the  operation  and  it  shall  be 
heated  to  a  low  cherry  red  only. 

13.  Vertical  stirrups  shall  always  pass  under  the  main  tension  bars,  or  be  rigidly  attached 
thereto. 

14.  For  all  floor  steel,  column  spirals  and  wherever  else  it  is  practicable,  mechanical  means 
shall  be  provided  for  holding  the  reinforcing  bars  in  place. 

15.  Reinforcing  steel  shall  be  clean,  free  from  scale,  grease,  paint,  oil  and  rust  (except  a  thin 
film  of  red  rust,  easily  rubbed  off  with  the  fingers).     The  Engineer  may  require  rods  to  be 
cleaned,  wherever,  in  his  opinion,  it  is  necessary. 

16.  Unless  otherwise  shown  on  plans,  all  splices  in  steel  shall  be  made  by  lapping  a  sufficient 
amount  to  develop  the  stress  in  the  bar  without  exceeding  the  allowable  adhesive  stress  as  given 
in  Section  III. 

17.  Reinforcing  bars  shall  be  wired  together  at  splices  and  as  far  as  practicable  shall  be  so 
arranged  as  to  provide  continuous  contact  between  the  bars,  the  purpose  being  to  minimize  the 
danger  from  electrolysis. 

18.  As  far  as  practicable,  electrical  conduits,  outlet  boxes  or  other  apparatus,  shall  not  come 
into  contact  with  the  reinforcing  bars. 

19.  Whenever  practicable,  concrete  inserts  shall  not  be  placed  in  contact  with  reinforcing 
bars. 

20.  When  long  anchor  bolts  for  setting  machinery,  etc.,  are  required  to  be  set  in  concrete 
before  pouring,  there  shall  be  provided  metal  sleeves  equal  in  length  to  one-half  the  length  of 
bolt  and  \T/2  inch  greater  in  diameter,  set  flush  with  the  surface  of  the  concrete  to  allow  some 
adjustment  of  the  bolts.    All  such  anchor  bolts  and  sleeves  are  to  be  set  by  means  of  templates. 

21.  The  Contractor  shall  furnish  the  Engineer  with  duplicate  copies  of  all  orders  for  rein- 
forcing steel  and  duplicate  copies  of  bending  and  marking  diagrams,  which  shall  be  approved  in 
writing  by  the  Engineer  before  work  is  begun. 


30 


Watson's  Bridge   Specifications  Section  VIII 


Placing  Concrete  in  Cold  Weather 


1.  Concrete  shall  not  be  placed  in  freezing  weather  except  by  special  arrangement  with  and 

under  the  supervision  of  the  Engineer  in  charge. 

2.  Mixing  water  having  a  temperature  of  less  than  60°  Fahr.  shall  not  be  used. 

3.  When  the  temperature  is  below  40°  Fahr.,  the  mixing  water  shall  be  heated  to  at  least 
100°  Fahr. 

4.  When  the  temperature  is  below  30°  Fahr.,  the  mixing  water  shall  be  heated  as  before, 
and,  in  addition,  the  aggregates  shall  be  heated  before  using,  and  the  work  properly  protected  by 
covering. 

5.  No  supports  shall  be  removed  from  concrete  poured  at  a  temperature  below  40°,  and  no 
load  allowed  to  be  carried  by  same,  until  it  shall  have  been  thoroughly  cured  and  dried  by  artificial 
heat. 

6.  No  concrete  shall  be  poured  at  a  temperature  below  20°  Fahr.,  without  such  additional 
precautions  as  may  be  required  by  the  Engineer  in  charge. 

7.  In  general,  the  use  of  salt  or  calcium  chloride  will  be  allowed  only  for  massive  concrete 
work,    and    then    only    by    written    permission    of    the    Engineer    in    charge.       If    used,    salt 
shall  be  No.  2  grade  common,  and  shall  equal  in  amount  .002%  by  weight  of  water  for  each  degree 
of  temperature  (Fahr.)  under  32°.    The  salt  shall  be  thoroughly  dissolved  in  the  mixing  water, 
the  amount  specified  being  equivalent  to  YI  Ib.  of  salt  for  each  barrel  of  4  cu.  ft.  capacity  and  for 
each  degree  of  temperature  below  32°  Fahr. 

8.  In  addition  to  the  above  requirements,  the  Engineer  may,  at  his  discretion,  require  the 
use  of  10  %i  excess  of  cement. 

9.  For  concrete  work  in  cold  weather,  the  use  of  quick  setting  cements  is  preferable,  and 
the  amount  of  mixing  water  should  not  be  greater  than  actually  required  for  proper  placing  and 
setting. 

10.  All  precautions  specified  shall  be  at  the  Contractor's  expense  unless  otherwise  stated  in 
the  contract. 

11.  Concrete    shall    not   be    poured    against    steel   forms    exposed   to   the  weather   when 
the  temperature  is  below  30°  Fahr. 


31 


Watson's  Bridge   Specifications  Section  IX 


Forms  and  Centers 


STRENGTH 

1.  All  forms  for  molded  concrete  work  shall  be  constructed  of  sufficient  strength  to  obtain 
the  necessary  rigidity  to  prevent  motion  of  the  forms  while  concrete  is  being  placed  and  shall  be 
strong  enough  to  carry  any  load  which  may  come  upon  the  concrete  within  thirty  days  from  the 
date  of  pouring. 

MATERIAL,  ETC. 

2.  Forms  shall,  in  general,  be  composed  of  tongue  and  grooved  or    square    edge    sheeting, 
properly  held  by  joists,  studding,  posts  and  bracing  against  the  concrete  surfaces.    Sheeting  shall 
be  as  nearly  as  possible  watertight  and  shall  be  surfaced  on  the  side  next  the  concrete  for  all 
surfaces  which  will  be  exposed  in  the  finished  work,  unless  otherwise  specified. 

3.  Forms  shall  be  constructed  by  experienced  and  capable  workmen  only,  and  shall  be  true 
to  line  and  grade  and  of  first-class  workmanship  throughout. 

4.  When  concrete  is  to  be  plastered,  rough  sheeting  shall  preferably  be  used. 

5.  Sheeting  lumber  which  is  used  more  than  once   shall  be  carefully  cleaned  after  each 
usage. 

6.  Great  care  must  be  taken  to  clean  all  saw  dust,  dirt  or  debris  from  forms  just  before 
placing  concrete,  and  whenever  necessary,  forms  shall  be  cleaned  out  by  steam    jet  or    equally 
effective  means.    All  forms  shall  be  so  constructed  as  to  be  readily  cleaned. 

7.  Lubricated  or  oiled  forms  shall  not  be  used  for  surfaces  that  are  to  fee  plastered^  painted 
or  colored,  or  against  surfaces  to  which  other  concrete  is  to  be  bonded. 

REMOVAL  OF  FORMS 

8.  Centers  shall  not  be  struck  from  under  arches  in  less  than  28  days,  except  in  the  case  of 
arch  culverts  of  less  than  30  foot  span. 

9.  In  general  forms  shall  not  be  removed  from  concrete  in  less  than  14  days  of  good  setting 
weather  at  a  temperature  over  50°  Fahr.,  except  in  the  case  of  vertical  surfaces,  etc.,  which  do  not 
carry  loads,  the  forms  for  which  may  be  removed  in  from  3  to  6  days. 

10.  Forms  shall  not  be  removed  from  under  concrete  which  has  been  poured  at  a  tempera- 
ture under  50°  Fahr.,  without  first  determining  if  the  concrete  has  properly  set,  without  regard  to 
the  time  element. 

11.  Forms  shall  always  be  removed  from  columns  before  removing  shores  from  beneath 
beams  and  girders,  in  order  to  determine  the  condition  of  the  column  concrete. 

12.  No    forms    whatever    shall    be    removed    at    any    time    without    first    notifying    the 
Engineer  in  charge,  who  shall  ascertain  if  the  concrete  be  set  sufficiently  hard  and  so  notify 
the  Contractor.    Such  notification  shall  not  be  considered  to  relieve  the  Contractor  of  respon- 
sibility for  the  construction  and  for  the  removal  of  such  forms. 

13.  All  forms  shall  be  designed  so  that  they  may  be  removed  with  as  little  damage  as 
possible  to  the  concrete  or  to  the  forms. 

32 


Watson's  Bridge   Specifications  Section  IX 

STEEL  FORMS 

14.  When  steel  forms  are  used,  all  bolt  and  rivet  heads  shall  be  countersunk  on  the  side 
against  the  concrete,  unless  otherwise  specifically  arranged  with  the  Engineer,  and  the  several 
pieces  must  join  together  neatly.    All  surfaces  must  be  true,  free  from  bends  or  other  irregulari- 
ties and  free  from  open  holes. 

15.  When  steel  forms  are  used  in  freezing  weather,  they  shall  be  covered  with  canvas  or 
otherwise  protected  from  the  weather.    Pouring  of  concrete  against  unprotected  steel  forms  in 
freezing  weather  will  not  be  allowed. 

TIMBER  FORMS. 

16.  In  constructing  timber  centers  for  arches  of  more  than  30  foot  span,  all  main  members 
shall  be  bolted  together  at  joints. 

17.  In  constructing  timber  centers  for  arches,  an  allowance  for  settlement  shall  be  made 
equal  to  %  inch  for  each  30  feet  vertical  height. 

GENERAL 

18.  The  Contractor  shall  furnish  the  Engineer  with  duplicate  copies  of  plans  for  forms  and 
centers,  which  must  be  approved  in  writing  by  the  Engineer  before  work  is  begun. 

19.  Wherever  practicable,  edges  of  beams,  girders  and  columns  shall  be  chamfered  and 
sides  of  beams  and  girders  shall  be  splayed  slightly  in  order  that  forms  may  be  more  readily 
removed. 

20.  All  projecting  wires  and  bolts  or  other  devices  that  are  used  for  holding  forms  and  that 
pass  through  the  concrete  shall  be  cut  off  at  the  surface  and  the  ends  depressed  with  a  nail  set. 

21.  In  proportioning  forms  and  centering,  concrete  shall  be  treated  as  a  liquid  of  its  full 
weight  for  vertical  loads  and  one-half  its  weight  for  horizontal  pressures. 

22.  Wedges  shall  have  a  slope  of  1  to  10. 

23.  Forms  for  beams  and  girders  shall  be  cambered  %  mcn  f°r  each  20  foot  span. 

24.  Forms  for  flat  slab  system  of  construction  shall  be  cambered  %  mcn  f°r  each  10  foot 
span  ;  camber  to  start  at  the  edge  of  the  column  head. 

25.  The  use  of  shims  shall  be  avoided  as  much  as  possible  and  when  shores  carry  heavy 
loads,  hardwood  shims  and  wedges  may  be  required  at  the  discretion  of  the  Engineer. 

26.  In  the  removal  of  forms  from  buildings,  the  Engineer  in  charge  may  require  reshor- 
ing,  wherever,  in  his  opinion,  it  is  necessary,  and  all  such  shores  shall  be  wedged  to  a  tight 
bearing  and  be  thoroughly  braced. 


27.     Forms  for  columns  shall  be  built  up  of  1^  inch  plank  and  stayed  at  intervals  of  not 
more  than  18  inches  vertically,  by  bands  or  straps  ;  or  steel  forms  may  be  used. 


33 


Watson's  Bridge   Specifications  Section    X 


Surface   Finish 


1.  The  surface  finish  for  all  exposed  parts  of  the  structure  will  be  called  for  on  the  plans, 
and  the  character  of  finish  desired  will  be  indicated  by  initialing  as  follows : 

"W"  indicates  a  cement  wash 

"S"  "  "  scrubbed  finish 

"R"  "  "  rubbed  finish 

"T"  "  "  tooled  finish 

"M"  "  "  mortar  facing 

"P"  "  "  plastered  surface 

"SB"  "  sand  blasted  surface 

"C"  "  "  colored  surface 

2.  If  no  surface  finish  be  called  for,  a  special  flat  tool  shall  be  worked  between  the  concrete 
and  the  sheeting  to  force  back  the  coarse  aggregates   and   produce   a   mortar    face,   then,    after 
removal  of  the  forms,  the  entire  surface  shall  be   gone   over   and   all   cavities,   etc.,   filled   with 
mortar  of  the  same  proportions  as  used  in  the  original  work,  the  mortar  being  forced  into  the 
cavities  by  pressure.    All  fins  and  projections  exceeding  ^  inch  shall  be  removed  by  tooling.    All 
surfaces  that  have  been  disturbed  either  by  closing  cavities   or   tooling   to   remove  projections, 
shall  be  rubbed  down  to  obtain  a  uniform  color. 

3.  For  all  kinds  of  finish,  the  surface  shall  be  gone  over  immediately  after  the  removal  of 
the  forms  and  all  loose  stone  and  defective  places  cleaned  out,  wires  and  rods  cut  off  at  surface 
and  depressed  with  nail  set,  and  then  all  holes  and  cavities   shall  be   filled  with  mortar  of  the 
same  mix  as  used  in  the  body  of  the  work.    Projecting  fins  and  inequalities  due  to  bulging  of 
forms,  etc.,  shall  be  removed  by  tooling,  as  directed  by  the  Engineer  in  charge. 

4.  CEMENT  WASH  FINISH  shall  consist  in  the  application  to  the  surface  of  a  thin 
cement  grout,  composed  of  one  part  cement  to  one  part  fine  sand,  applied  with  a  brush  and  imme- 
diately rubbed  in  with  a  wooden  float. 

5.  SCRUBBED  FINISH  shall  be  obtained  by  removing  the  forms  as  soon  as  practicable 
and  washing  away  the  cement  film  on  the  surface  by  means  of  a  scrubbing  brush  and  water, 
exposing  the  aggregates.    If  the  cement  has  set  so  that  it  cannot  be  washed  out  with  water,  then  a 
weak  solution  of  hydrochloric  or  muriatic  acid  shall  be  used,  the  surface  being  thoroughly  rinsed 
off  afterwards. 

6.  RUBBED  FINISH  shall  be  obtained  by  rubbing  down  the  surface  with  a  piece  of  carbor- 
undum brick,  or  other  abrasive,  sufficiently  to  remove   all   marks   of   timber   forms  and   other 
irregularities.    The  surface  to  be  rubbed  shall  be  wet,  and  a  thin  grout,  composed  of  one  part 
cement  to  one  part  fine  sand,  brushed  in  during  the  rubbing.    The  rubbing  shall  always  be  the  final 
operation.    A  finish  application  of  the  cement  grout  will  not  be  allowed.    The  cement  grout  may 
be  omitted  entirely  by  direction  of  the  Engineer  in  charge. 

7.  TOOLED  FINISH  shall  be  obtained  by  removing  the  surface  mortar  a  sufficient  amount 
to  expose  the  aggregates,  by  means  of  stone  dressing  tools,  as  called  for  on  plans.    Unless  other- 
wise specified,  the  surface  shall  be  dressed  to  a  smooth  finish  equal  to  fine  pointed  or  crandalled 
work  in  stone  masonry.     Cast  stone  surfaces,  when  tooled,  shall  be  ground  out  in  parallel  lines 
by  revolving  carborundum  wheels  or  equally  effective  means,  using  eight  cuts  to  the  inch,  unless 
otherwise  specified. 

34 


Watson's  Bridge   Specifications  Section  X 

8.  MORTAR  FACE  FINISH,  if  called  for,  shall  consist  of  a  facing,  not  less  than  1  inch 
thick,  composed  of  specially  selected  materials,  which  shall  be  as  uniform  as  possible  for  the  entire 
job,  and  proportioned  so  as  to  be,  as  nearly  as  practicable,  of  the  same  strength  and  consistency 
as  the  backing.     The  surface  finish  of  the  mortar  face  shall  be  as  indicated  on  the  drawings. 

9.  PLASTERED  SURFACES  shall  be  obtained  by  plastering  a  coat  of  mortar  on  a  back- 
ing of  concrete.    The  surface  of  the  backing  shall  be  rough,  in  order  to  give  sufficient  bond  and 
the  mortar  shall  be  thoroughly  trowelled  on.    Plastering  shall  only  be  done  by  skilled  labor. 

10.  SAND  BLAST  FINISH  shall  be  obtained  by  means  of  the  sand  blast  on  thoroughly 
hardened  surfaces  only,  using  crushed  quartz  or  other  hard  material.    All  cavities  shall  be  filled 
and  pronounced  projections  removed  before  using  the  sand  blast.     Mouldings,  sharp  edges,  etc., 
must  be  properly  protected  from  the  blast. 

11.  COLORED  SURFACES  will  be  used  only  when  specifically  called  for  on  the  draw- 
ings and  described  in  detail.     Only  mineral  colors  shall  be  used. 


35 


Watson's   Bridge    Specifications  Section  XI 


Waterproofing 


1.  Concrete,  which  is  desired  to  have  water-resisting    qualities,    shall,    unless    otherwise 
specified,  be  No.  6  mix,  of  carefully  graded  materials  so  that  the  percentage  of  voids  shall  be  as 
low  as  practicable,  and  shall  be  laid  as  nearly  monolithic  as  possible. 

2.  Waterproofing  will  be  divided  into  four  classes,  as  follows : 

1.  Integral  Method  (I.  W.  P.)  — Mixing  foreign  substances  with  the  concrete. 

2.  Membrane  Method  (M.  W.  P.)  — Protecting  the  concrete  surface  by  means  of  an 

independent    waterproof    layer,    usually    of 
fabric  impregnated  with  bitumen. 

3.  Bituminous  Mastic  Method  (A.  W.  P.) — Applying  a  coating  of  bituminous  mastic  to  the 

surface  to  be  waterproofed. 

4.  Coating  Method  (D.  P.)  — Applying    bitumen    or    other    waterproofing 

material  directly  to  the  concrete  surface. 

3.  The  method  to  be  used  shall  be  shown  on  the  drawings,  by  marking  as  above  indicated. 

INTEGRAL  METHODS 

4.  When  waterproofing  by  the  integral  method  is  called  for,  it  shall  be  done  by  mixing  with 
the  cement  or  water  used  the  material  specified,  consisting  of  alum  and  soap  solution,  hydrated 
lime,  or  one  of  the  various  compounds  sold  for  this  purpose,  such  as  Toxment,  Ceresit,  Trus-con 
waterproofing  paste,  Medusa  waterproofing  compound,  etc. 

5.  If  alum  and  soap  be  specified,  a  5%  solution  of  ground  alum  and  water  shall  be  prepared, 
and  a  7%  solution  of  soap  and  water.     The  alum  solution  shall  be  mixed  with  the  mortar  to  the 
amount  of  one-half  the  ordinary  gaging  water.     The  soap  solution  shall  then  be  applied  in  amount 
required  to  obtain  the  desired  plasticity.     (From  Prof.  Hatt.) 

6.  If  hydrated  lime  be  called  for,  5%  by  weight  (of  the  weight  of  the  cement)  of  thoroughly 
hydrated  lime  shall  be  added  to  the  mixing  water  or  an  equivalent  amount  may  be  mixed  dry  with 
the  cement.    Care  shall  be  taken  to  insure  that  the  lime  be  completely  hydrated.     Hydrated  lime 
shall  pass  the  Standard  Specifications  for  hydrated  lime  of  the  American  Society  for  Testing 
Materials,  and  shall  be  of  the  class  known  commercially  as  Calcium,  unless  otherwise  specified. 

7.  If  the  use  of  any  of  the  patented  compounds  be  called  for,  the  work  shall  be  done  in 
strict  accordance  with  the  instructions  issued  by  the  manufacturers  thereof. 

8.  The  integral  method  shall  not  be  used  with  a  leaner  mixture  than  1-2-4  (No.  6). 

9.  If  so  indicated  on  the  plans,  the  integral   waterproofing   method   may   be   used    for   a 
mortar  coat  applied  to  the  body  of  the  concrete,  which   shall   be   1   inch   thick   unless   otherwise 
specified,  and  mixed  1  to  2. 

10.  When  the  character  of  the  integral  method  is  not  shown  on  the  drawings,  either  Toxment, 
Ceresit,  Trus-con  or  Medusa  compound  shall  be  used,  or  other  material  may  be  substituted  with 
the  permission  of  the  Engineer. 

MEMBRANE  METHODS 

11.  The  membrane  method  shall  consist  of  alternate  layers  of  cementing  material  or  binder 
and  fabric,  the  first  and  final  layer  being,  in  all  cases,  composed  of  the  binder.     The  number  of 
layers,  or  ply,  shall  refer  to  the  number  of  layers  of  fabric  used  and  shall  be  as  indicated  on  the 
drawings.    The  binder  shall  be  either  asphalt  or  coal  tar  pitch,  as  specified. 

36 


Watson's   Bridge    Specifications  Section  XI 

12.  Unless  otherwise  shown  on  the  drawings,  the  number  of  plies  will  be  as  follows : 

Class  A  Class  B  &  C 

For  head  of    0  feet  1  2 

"      "      "    1  foot  2  3 

"      "      "    2  feet  3  4 

"       "       "     6  feet  4  5 

"       "       "     8  feet  5  6 

"       "       "  10  feet  6  7 

"       "       "  15  feet  7  8 

"      "      "  20  feet  8  9 

13.  The  entire  waterproofing  course  shall  be  flexible,  pliable  and  elastic  between  150°  F. 
and  0°  F.    All  expansion  joints  and  cracks  in  the  concrete  surface  shall  be  covered  by  specially 
designed  joints.    At  such  joints  and  cracks  the  membrane  shall  not  be  cemented  to  the  concrete 
for  a  distance  of  at  least  12  inches  on  each  side  of  such  joint  or  crack. 

14.  Each  strip  of  fabric  shall  lap  2  inches  over  the  preceding  strip,  and  the  strips  of  alter- 
nate plies  shall  lap  one-half  the  width  of  the  strip.     Each  layer  or  ply  shall  alternate  with  the 
preceding  layer  in  the  direction  of  laying.     Each  layer  shall  be  applied  to  the  binder  while  the 
latter  is  still  hot  and  pressed  against  it  so  as  to  insure  its  being  completely  stuck  to  the  binder  over 
the  entire  surface.    All  end  laps  shall  be  at  least  10  inches.     The  binder  shall  completely  cover 
the  surface  on  which  it  is  laid  without  cracks  or  blowholes.    The  first  coat  (except  the  cement- 
ing coat,  if  used)  shall  be  a  binder  coat,  and  the  final  coat  shall  always  be  a  binder  coat. 

15.  The  surfaces  to  be  waterproofed  shall  be  dry  and  free  from    sharp    projections.      All 
corners  and  angles  shall  be  waterproofed  without  cutting  or  slitting  the  fabric.    Flashing  shall 
be  carefully  done  around  all  openings  and  obstructions. 

ASPHALT  AND  CLOTH  FABRIC  WATERPROOFING— CLASS  "A" 

16.  The  cloth  fabric  shall  be  thoroughly  saturated  with  the  bituminous  material  with  which 
it  is  applied  or  cemented  together,  so  that  when  an  individual  strand  is  split,  the  center  of  the 
strand  shall  be  black  with  the  saturant.     It  must  be  flexible  and  elastic    at   all    temperatures 
between  0°  and  250°  Fahr.,  and  have  a  stretch  in  two  directions  of  at  least  5%  without  fracture. 

17.  A  1  inch  strip  shall  have  a  tensile  strength  of  at  least  100  Ibs.     It    must    stand    a 
puncture-proof  test  of  100  Ibs.  to  the  square  inch.    It  must  not  crack  or  flake  when  folded  back 
on  itself  and  creased  at  the  fold,  irrespective  of  temperature.     It  must  be  unaffected  by  all  acids 
and  alkalies ;  that  is  be  chemically  inert. 

18.  The  material  with  which  the  cloth  is  to  be  applied  (sometimes  called  the  binder)  shall 
be  a  naturally  occurring  asphaltic  bitumen,  at  least  96%  of  which  shall  be  pure  hydro-carbon.    It 
shall  have  a  melting  point  of  approximately  200°  Fahr.  and  shall  be  flexible  at  0°  Fahr.    It  shall 
volatilize  not  more  than  1%  upon  heating  for  5  hours  at  325°  Fahr.  in  an  open  Cleveland  cup.    It 
shall  be  unaffected  by  25%  solutions  of  hydrochloric  or  sulphuric  acid  or  saturated  solutions  of 
alkalies  and  brine.    It  shall  have  strong  adhesive  qualities  and  bond  firmly  to  the  concrete  to 
which  it  is  applied.    It  shall  be  refined  by  direct  heat  and  not  by  the  "blown"  process. 

19.  The  surface  to  be  waterproofed  shall  be  carefully  cleaned  and  dry  and  shall  have  a  coat 
of  liquid  asphalt  paint  to  serve  as  a  bonding  coat,  applied  with  a  brush  before  the  first  mop  coat, 
unless  the  plans  call  for  the  omission  of  the  priming  coat. 

37 


Watson's  Bridge    Specifications  Section  XI 

PITCH  AND  FABRIC  WATERPROOFING— CLASS  "B" 

20.  The  fabric  shall  be  the  same  as  specified  in  Paragraphs  16  and  17,  saturated  with  coal 
tar  pitch. 

21.  The  binding  material  and  saturant  shall  be  straight  run  coal  tar  pitch  distilled  direct 
from  American  coal  tar.    The  pitch  shall  have  a  melting  point  of  from  130°  to  140°  Fahr.,  and 
be  applied  at  a  temperature  of  not  less  than  250°  Fahr. 

PITCH  AND  FELT  WATERPROOFING— CLASS  "C" 

22.  The  felt  shall  weigh  not  less  than  14  Ibs.  per  100  sq.  ft.,  single  thickness,  and  shall  be 
thoroughly  saturated  with  the  pitch. 

23.  The  saturant  and  binder  shall  be  the  same  as  specified  in  Paragraphs  18  or  21. 

BITUMINOUS  MEMBRANE  WATERPROOFING— CLASS  "D" 

24.  Waterproofing  of  this  class  shall  be  similar  to  that  specified  for  Class  "C,"  except  that 
there  shall  be  not  less  than  three  plies,  the  center  ply  being  a  cloth  fabric  equal  to  that  specified 
in  Paragraph  16,  the  remaining  plies  being  felt. 

BITUMINOUS  MASTIC  WATERPROOFING 

25.  After   the   cement   concrete   in   the   structure   has   thoroughly   dried,   the   entire  top 
surface  to  be  waterproofed  shall  be  painted  with  the   asphalt  hereinafter   specified,   melted   and 
diluted  with  62°  Beaume's  naphtha  to  the  proper  consistency. 

26.  The  surface  so  prepared  shall  then  be  waterproofed  with  asphalt  mastic  equal  in  quality 
to  the  following  specification: 

Neuf  chatel  Seyssel  or  Sicilian  Rock  Asphalt  Mastic  60  parts 

Clean,  sharp  graded  grit  and  sand  to  pass  sieve  of  8  meshes  per  inch ....  30  parts 

Refined  Bermudez  or  Trinidad  Asphalt 10  parts 

These  proportions  shall  be  varied  where  required  by  special  conditions  of  the  work. 

27.  The  mixture  shall  be  made  at  the  site  of  the  work,  and  heated  to  a  temperature  of  from 
250  to  300°  F.  and  stirred  until  all  the  ingredients  are  thoroughly  incorporated.     It    shall    be 
spread  and  thoroughly  worked  to  free  it  from  voids  and  ironed  to  a  smooth,  dense  surface  with 
hot  smoothing  irons,  if  so  directed. 

28.  The  waterproofing  shall  be  applied  in  two  coats;  each  finished  coat  shall  be  24  of  an 
inch  in  thickness.    The  different  coats  shall  break  joints  and  the  mastic  be  distributed  evenly. 

COATING  OR  DAMPPROOFING 

29.  When  one  or  more  coats  of  dampproofing  are  called  for  on  the  plans,  there  shall  be 
applied  to  the  surface  natural  asphalt  or  coal  tar  pitch  of   sufficient  body  to  completely  fill  all 
pores  in  the  concrete.    Such  pitch  shall  be  applied  hot,  if  necessary,  and  the  surface  to  be  water- 
proofed shall  be  clean  and  dry. 

30.  If  proprietary  compounds  are  called  for,  they    shall   be   applied    in   accordance   with 
directions  from  the  manufacturers. 

31.  In  dampproofing  basement  walls,  etc.,  the  Engineer  may  require  the  walls  to  be  first 
plastered  if  the  surface  is  not  smooth  enough  to  receive  the  dampproofing  properly. 

38 


Watson's   Bridge   Specifications  Section  XI 

32.  If  it  be  necessary  to  dampproof  wet  concrete,  a  special  binder  shall  be  used  to  bond  the 
pitch  to  the  concrete. 

GENERAL 

33.  All  surfaces  waterproofed  by  the  membrane  method,  and  which  are  to  be  covered  with 
an  earth  fill,  such  as  basement  walls,  etc.,  shall  have  the  waterproofing  protected  by  a  course  of 
brick  or  a  1  inch  plaster  coat  of  1  to  3  mortar,  before  applying  the  back  fill  or  covering. 

34.  Especial  care  shall  be  taken  to  provide  proper  laps  at  the  juncture  of  floors  and  walls, 
when  using  the  membrane  method.    These  laps  shall  be  at   least    1    foot   wide    and    thoroughly 
protected  from  damage. 

35.  All  concrete  surfaces  to  be  waterproofed  shall  be  trowelled  to  a  smooth  finish.     This 
work  shall  be  done  by  the  Contractor  for  the  concrete  work. 

36.  All  waterproofing  shall  be  carefully  protected  from  injury.     Where  brick  or  concrete 
protection  is  shown  on  the  plans,  it  shall  be  laid  by  the   Contractor   for  waterproofing,   and  the 
materials  shall  be  furnished  by  the  mason  or  concrete  Contractor,  unless  otherwise  arranged. 


39 


Watson's  Bridge   Specifications  Section  XII 


Reinforced  Steel  Construction 


1.  When  the  steel  reinforcement  is  so  designed  that  it  will  carry  in  itself,  without  support 
from  the  encasing  concrete,  a  definite  proportion  of  the  loads,  all  parts  of  the  steel  construction 
shall  be  designed  to  carry  such  proportion  of  the  loads,  using  the  specifications  of  The  American 
Railway  Engineering  Association. 

2.  In  addition  to  its  portion  of  the  specified  loads,  the  steel  frame  shall  also  be  proportioned 
to  provide  for  all  bending  stresses  due  to  the  negative  bending  moment,  in  the  case  of  partially 
continuous  construction,  or  the  bending  moments  due  to  eccentric  loads,  etc. 

3.  The  steel  shall  be  proportioned  to  resist  all  tensile  stresses  due  to  the  full  load. 

4.  The  concrete  shall  be  so  proportioned  as  to  provide  the  additional  compressive  resistance 
required  for  the  balance  of  the  load,  in  conformity  with  the  requirements  of  the  other  sections 
of  these  specifications. 

5.  Unless  special  provision  is  made  to  develop  continuity,    all    beams    and    girders    of 
reinforced  steel  construction  shall  be  computed  as  simple  beams. 

6.  Forms  for  reinforced  steel  beams,  girders  and  columns  may  be  removed  in  one-half  the 
time  specified  for  monolithic  reinforced  concrete  construction  when  the  steel  frame  is  propor- 
tioned to  carry  the  full  dead  load  then  in  place  without  assistance  from  the  concrete. 

7.  In  reinforced  steel  construction  the  occurrence  of  large  flat  surfaces  of    steel    shall    be 
avoided    as    far    as    practicable,    and    in    no    case  shall  a  single  surface  exceed  6  inches  for 
horizontal  surfaces  covered  with  concrete,  or  else  soffit  clips  or  other  satisfactory  devices  for 
securing  adhesion  of  the  concrete  to  the  steel  shall  be  provided. 

8.  All  horizontal  surfaces  of  steel  shall  be  covered  with  concrete  not  less  in  thickness  than 
one-half  the  width  of  the  surface  so  covered,  and  shall  be  wrapped  with  expanded  metal  or  wire 
cloth,  when  exceeding  4  inches  in  width. 

9.  Angles  placed  back  to  back  shall  be  separated  a  distance  at  least  twice  the  maximum 
diameter  of  stone  used  in  the  concrete. 

10.  Compression  members  encased  in  concrete  shall  be  stressed  not  more  than  fifteen  times 
the  stress  in  the  concrete,  except  where  part  of  the  stress  is  developed  in  the  steel  prior  to  the  plac- 
ing of  the  concrete,  in  which  case  the  increment  of  stress  after  placing  the  concrete  shall  not 
exceed  fifteen  times  the  stress  in  the  concrete,  nor  shall  the  total  unit  stress  exceed  the  allowed 
tensile  unit  stress. 

11.  Unit  stresses  shall  be  as  follows : 

Tension,  net  section,  rolled  steel 16000 

Direct  compression,  rolled  steel  and  steel  castings  (not  columns) 16000 

Bending,  on  extreme  fibers  of  rolled  shapes,  built  sections,  girders  and 

steel  castings 16000 

Bending  on  extreme  fibers  of  pins 24000 

Shear  on  shop  rivets  and  pins 12000 

Shear  on  bolts  and  field  rivets : 10000 

Shear — average — on  webs  of  plate  girders  and  rolled  beams,  gross  section. .  10000 

Bearing  pressure  on  shop  rivets  and  pins 24000 

Bearing  on  bolts  and  field  rivets 20000 

40 


Watson's  Bridge   Specifications  Section  XII 

The  pressure  per  linear  inch  on  expansion  rollers  shall  not  exceed  600  times  the  diameter  of 
rollers  in  inches. 

Axial  compression  on  gross  sections  of  columns  for 

ratio  of  —  up  to  120        16000  —  70  —  with  a  maximum  of  14000 

r       f  r 

where  1  =  effective  length  of  members  in  inches,  using  full  length  for  abutting  ends 
and  one-half  full  length  for  fixed  ends. 

r  =  corresponding  radius  of  gyration  of  section  in  inches. 

12.  Steel  to  be  encased  in  concrete  shall  not  be  painted,  unless  otherwise  provided  for,  but 
shall  be  free  from  rust,  scale,  grease  or  dirt. 

13.  Unless  otherwise  specified,  all  connections  shall  be  riveted. 

14.  Satisfactory  provision  shall  be  made  for  wind  bracing  during  erection  of  steel  work. 

15.  All  structural  material  shall  be  subject  to  inspection  and  tests  at  mill  and  shop,  and  no 
material  shall  be  shipped  until  so  inspected  and  accepted. 

16.  Reinforced  steel  columns  shall  preferably  be  of  the  "Gray"  or  other  type  of  open 
section. 

17.  In  proportioning  reinforced  steel  columns,  no  direct  allowance  shall  be  made  for  the 
concrete  in  compression,  unless  it  be  secured  by  hooping,  but  in  such  columns  the  unit  stress 
on  the  steel,  assuming  the  steel  to  carry  the  entire  load,  may  be  taken  at  16000  Ibs.  per  square 

inch  when  the  ratio  of  — r-  =  15. 
d      < 

18.  When  the  concrete  encasing  structural  steel  columns  is  provided  with  hooping  as  pro- 
vided for  in  Section  III,  Paragraphs  10  and  11,  the  column  may  be  proportioned  as  therein  pro- 
vided for,  using  650  Ibs.  per  square  inch  working  stress  on  the  concrete  (No.  6)  and  10000  Ibs. 
per  square  inch  on  the  steel,  assuming  the  spiral  steel  as  equivalent  to  2.4  times  its  volume,  taken 
as  vertical  steel. 


41 


Watson's   Bridge    Specifications  Section  XIII 


Cast  Stone  and  Blocks 


1.  Cast  Stone  work  includes  facing  blocks,  parapets,   railings   and  ornamental    work    con- 
structed of  separately  molded  or  cast  blocks  of  concrete. 

2.  Cast  Stone  shall  preferably  be  cast  in  a  sand  mold   in   an   established   factory,   and   all 
exposed  surfaces  shall  be  dressed  by  hand,  by  means  of  revolving  carborundum  wheels,  or  similar 
devices  used  in  such  factories  to  produce  tooled  or  other  good  stone  finish.     At  least  1/12  inch 
of  such  surfaces  shall  be  removed. 

3.  When  any  Cast  Stone  exceeds  in  any  dimension  six  times  its  least  dimension  it  shall  be 
properly  reinforced  to  insure  safety  in  handling,  such  reinforcement  to  be  not  less  than  .5%  of 
the  cross  section  at  right  angles  to  the  line  of  reinforcement,  unless  the  reinforcement  be  shown 
on  the  drawings. 

4.  The  proportion  of  cement  to  aggregate  in  Cast  Stone  and  Blocks  must  not  be  less  than 
1  to  6  nor  greater  than  1  to  4  and  the  aggregate  must  not  be  too  fine  but  shall  be  of  graded  sizes 
from  y%  inch  diameter  down  when  screened  aggregate  is  used. 

5.  Aggregates  for  Cast  Stone  shall  preferably  be  made  by  crushing  whole  pieces  of  such 
material  as  granite  and  marble  and  not  over  40%  should    pass  a    1/16    inch    mesh    screen. 
Aggregates  should  be  mixed  with  the  cement  in  a  mixer,  preferably  of  the  rotary  type,  with  not 
less  than  15%  of  water  by  weight.    If  it  is  to  be  cast  in  sand  molds  it  shall  be  constantly  agitated 
from  the  time  it  is  removed  from  the  mixer  until  it  is  distributed  in  the  mold. 

6.  Building   Blocks   shall   be   used   wherever  shown  on  the  drawings  and  shall  be  well 
cured  and  dense,  with  good  edges,  shall  show  a  strength  of  at  least  1,000  Ibs.  per  square  inch  at 
28  days  and  an  absorption  of  not  over  5%  by  weight  when  thoroughly  dried  and  immersed  in 
water  for  48  hours. 

7.  The  Contractor  shall  furnish  samples  of  the  concrete  Blocks  and  Cast  Stone  proposed 
to  be  used,  which  shall  be  satisfactory  to  the  Engineer,  and  the  Blocks  and  Stone  used  must  con- 
form in  every  way  to  such  samples. 

8.  No  broken,  chipped,  or  checked  blocks  or  castings  will  be  allowed  to  be  used  in  the  work 
and  all  blocks  or  castings  shall  be  carefully  protected  from  injury.    By  checked  blocks  are  meant 
blocks  showing  fine  hair  checks  on  the  surface. 

9.  All  cast  stone  must  be  provided  with  suitable  dowels  and  anchors  for  securing  same  to 
the  work  and  with  hooks  for  handling,  and  all  cast  stone  and  blocks  must  be  laid  up  in  white 
or  non-staining  Portland  cement  mortar,  when  mortar  is  used. 

10.  The  material  to  be  used  for  aggregates  and  the  finish  shall  be  as  indicated  on  the 
drawings. 

11.  All  cast  stone  shall  be  carefully  bedded  in  full  mortar  joints,  and  shall  be  cleaned  and 
wet  before  placing.    Joints  shall  be  3/16  inch  thick  and  allowance  made  for  same.    Joints  shall 
be  pointed  flush  at  the  time  blocks  are  laid  and  before  the  mortar  has  set. 

42 


Watson's  Bridge   Specifications  Section   XIII 

12.  Unless  otherwise  shown  on  the  drawings,  railings,  parapets  and  other  ornamental  work 
shall  be  composed  of  1  part  cement,  2  parts  selected   white    sand,    and   2   parts    crushed    silica 
gravel.    The  forms  shall  be  removed  as  soon  as  can  be  done  without  injury  to  the  concrete,  and 
the  surface  scrubbed  with  a  brush  and  clear  water,  until  the  aggregates  are  exposed,  using  acid  in 
the  water  if  necessary. 

13.  All  thin  sections  of  cast  stone  work  shall  be  reinforced  sufficiently  to  prevent  shrinkage 
cracks. 

14.  Cast  stone  railings  and  parapets  shall  have  expansion  joints  at  frequent  intervals,  and 
all  such  joints  shall  be  lined  with  asbestos  board,  or  other  material  which  will  not  adhere  to  con- 
crete nor  discolor  same. 


Watson's   Bridge    Specifications  Section  XIV 


Concrete  Piling 


1.  Concrete  piles  will  be  divided  into  two  classes  :  first,  concrete  piles  precast  and  driven  to 
place,  and  second,  concrete  piles  cast  in  place.     The  former   shall  be  sufficiently  reinforced  to 
withstand  handling  and  shall  be  provided  with  proper  cushions  for  driving  and  will  be  entirely  at 
Contractor's  risk.    They  shall  be  driven  to  elevations  as  given  by  the  Engineer  or  else  they  shall 
be  cut  off  to  such  elevations.     Piles  of  the  second  class  will  preferably  be  of  the  "Simplex," 
"Raymond,"  "Pedestal"  or  similar  patented  types,  as  indicated  on  the  drawings. 

FORMULAS 

2.  The  safe  bearing  power  of  concrete  piles  shall  be  determined  by  means  of  the  following 
formula,  for  straight  or  tapered  piles,  either  precast  or  cast-in-place,  when  not  driven  to  refusal. 

(a)     Using  drop  hammer  weighing  not  less  than  the  weight  of  the  pile  P  =  ^' 


(b)     Using  steam  hammer,  the  striking  parts  of  which  weigh  not  less  than  the  weight 
of  the  pile  P  =  j^p|f 

Where  P  =  working  load  in  tons 

W  —  weight  of  hammer  in  pounds 

H  —  fall  in  feet 

S  =  average  penetration  for  last  foot  in  inches 

(c)     When    the    weight    of    the    striking  parts   of   the  hammer   is   less   than  the 
weight  of  the  pile,  the  working  loads,  as  given  by  the  above  formula,  shall  be  increased 
by  multiplying  same  by  the  ratio  of  the  weight  of  the  pile  to  the  weight  of  the  striking 
part  of  the  hammer.     The  weight  of  striking  part  of  hammer  shall  equal  at  least 
one-half  the  weight  of  the  pile. 

TESTING 

3.  If  tests  are  called  for  in  the  contract,  the   Contractor  shall,   at  his  own   expense,   and 
under  the  direction  of  the  Engineer,  test  the  number  of  test  piles  called  for  by  the  plans,  which 
will  be,  in  general,  one  pile  for  each  different  condition  of  foundation  encountered,  by  loading 
to  one  and  one-half  times  the  specified  loads  without  exceeding  a  settlement  of   %   inch,  unless 
otherwise  specified  on  the  drawings  or  herein. 

CAST  IN  PLACE  PILES 

4.  If  piles  of  the  "Raymond"  type  be  used,  the  shell  shall  be  inspected  for  each  pile  before 
concrete  is  poured  and,  whenever  practicable,  no  pile  shall  be  filled  with  concrete  until  all  shells 
within  6  feet  of  same  shall  have  been  driven. 

5.  Piles  cast  in  place  shall  not  be  reinforced  unless  so  indicated  on  plans,  but  all  such 
piles  shall  be  provided  with  at  least  four  %  inch  dowel  bars  when  capped  with  concrete. 

PRECAST  PILES 

6.  Precast  piles  shall  always  be  reinforced  with  sufficient  steel  so  that  when  supported  at 
the  third  points  in  the  length,  the  stresses  in  the  reinforcement,  computed  in  accordance  with  the 
methods  prescribed  herein,  shall  not  exceed  the  allowed  unit  stresses  given. 

44 


Watson's   Bridge    Specifications  Section  XIV 

7.  In  addition  to  the  reinforcement  specified  above,  all  precast  piles  shall  be  provided  with 
dowels,  similar  to  those  molded  in  place,  unless  otherwise  specified  or  indicated  on  plans. 

8.  All  precast  piles  shall  be  provided  with  special   reinforcement,   or   other   means,   at  the 
top  to  give  greater  resistance  to  the  impact  of  the  hammer. 

9.  The  reinforcement  shall  be  carefully  centered  in  the  form,  and  provided  with  mechanical 
devices  for  holding  all  parts  rigidly  in  place  while  concrete  is  being  poured. 

10.  Care  shall  be  taken  to  thoroughly  ram  the  concrete  around  the  reinforcement. 

11.  Precast  piles  shall  be  provided  with  shoes  and  cushion  for  driving,  whenever  necessary, 
at  the  Contractor's  expense. 

12.  All  precast  piles  shall  be  seasoned  at  least  30  days  at  a  temperature  over  60°  Fahr.  before 
driving. 

GENERAL 

13.  The    number    of    piles    required    may    be    changed    by    the    Engineer,    at    his    dis- 
cretion,   and    such    change    shall    not    affect   the  price  per  lineal   foot  bid,  provided  that  the 
change  does  not  exceed  25  %  of  the  total  length  of  piles,  and  in  the  case  of  lump  sum  bids,  the 
amount  to  be  paid  shall  be  to  the  amount  bid  in  the  proportion  of  the  total  length  of  piling  used, 
to  that  shown  on  the  plans,  provided  that  such  change  does  not  exceed  25  %  of  the  quantities 
shown  on  the  contract  drawings. 

14.  All  piles  shall  be  straight  and  a  variation  from  a  straight  line  exceeding  1  inch  in  24  feet 
shall  be  cause  for  rejection  of  the  piles.     No  allowance  will  be  made  for  the  side  pressure  of 
earth  in  holding  piles  in  line,  when  they  are  computed  and  loaded  as  concrete  columns. 

15.  The  maximum  allowable  load  on  concrete  piles,  not  reinforced  as  columns,  shall  not 
exceed  300  Ibs.  per  square  inch.    When  the  principal  resistance  to  settlement  is  from  the  side  or 
skin  friction  of  the  piles,  this  allowable  load  may  be  computed  upon  the  average  diameter  of  the 
imbedded  pile.    When  concrete  piles  act  as  columns,  the  allowable  load  shall  be  computed  upon 
the  minimum  cross-section  of  the  pile  and  the  design  of  such  piles  shall  be  in  accordance  with  the 
rules  for  designing  concrete  columns  given  herein. 

16.  Unless  otherwise  called  for,  all  concrete  used  in  piles  shall  be  No.  5^2  (1-2-3^),  the 
coarse  aggregates  being  1  inch  maximum  size. 

17.  No  allowance  shall  be  made  for  direct  bearing  on  rock  or  hard  pan  when  tapered  or 
pointed  piles  are  used. 

18.  No  piles  shall  be  loaded  eccentrically  nor  shall  any  concrete  pile  be  used  when  driven 
out  of  plumb  more  than   ^   inch  per   foot  of  length. 

19.  The  minimum  distance,  center  to  center,  of  piles  shall  be  not  less  than  3  feet. 

20.  Payment  shall  be  made  per  lineal  foot,  at  the  contract  prices  for  piles  furnished  and  for 
piles  driven. 


45 


Watson's   Bridge    Specifications  Section  XV 


Inspection  and  Tests 


1.  The  Engineer  will  have  an  Inspector  on  the  work,  whose  duties  will  be  to  see  that  these 
specifications,  the  plans  and  contract  are  correctly  interpreted  and  carried  out. 

2.  All  materials  shall  be  purchased  subject  to  thorough  inspection  and  tests  by  the  Engineer 
or  a  Laboratory  appointed  by  him. 

3.  Cement  shall  be  tested  in  accordance  with  the  methods  adopted  by  the  Committee  on 
Uniform  Tests  of  Cement  of  the  American  Society  of  Civil  Engineers,  and  no  cement  shall  be 
used  until  the  seven  day  test  shall  have  been  made.    Unless  otherwise  specified,  the  cost  of  test- 
ing cement  shall  be  paid  by  the  Owner. 

4.  Reinforcing  steel  shall  be  purchased  subject  to  tests  provided  for  in  the  Standard  Specifi- 
cations for  Steel  Reinforcing  Bars  of  the  American  Society  for  Testing  Materials.    Ladle  analyses 
shall  be  furnished  by  the  mill.    Tension  and  bending  tests  shall  be  made  from  each  melt. 

o.  Structural  steel  shall  be  purchased  subject  to  tests  provided  for  in  the  Standard  Specifi- 
cations for  Structural  Steel  for  Bridges,  adopted  by  the  American  Society  for  Testing  Materials. 
Ladle  analyses  shall  be  furnished  by  the  mill.  Tension  and  bending  tests  shall  be  made  from 
each  melt  by  or  in  the  presence  of  an  Inspector  representing  the  Owner. 

6.  When  the  Owner,  or  the  Engineer  so  notifies  the  Manufacturer,  tension  and  bending  tests 
shall  be  made  by  the  Manufacturer  and  copies  of  results  of  such  tests  furnished  the  Engineer. 

7.  Aggregates  shall  be  tested  by  the  Engineer,  or  by  a  Laboratory  designated  by  him,  and 
the  Contractor  shall  furnish,  free  of  charge,  sufficient  material  for  such  testing. 

8.  The  Contractor  shall,  at  the  request  of  the  Engineer  in  charge,  cast  standard  cubes  or 
cylinders  for  testing,  which  shall  be  tested  by  an  approved  Laboratory,  in  order  to  determine  the 
strength  of  the  concrete. 

9.  Unless  otherwise  specifically  agreed,  no  concrete  shall  be  poured  in  the  absence  of  the 
Inspector  representing  the  Engineer. 

10.  On  the  completion  of  the  work  and  before  it  has  been  accepted,  the  Engineer  may  cause 
final  tests  to  be  made  at  the  expense  of  the  Contractor,  provided  that  such  tests  are  called  for  in 
the  contract,  by  loading  a  typical  unit  of  the  structure  with  twice  the  specified  live  load  applied 
statically.     These  tests  will  not  be  made  on  concrete  which  has  had  less  than  sixty  days  of  good 
setting  weather  at  a  temperature  of   over   60°  Fahr.    The  static  load  shall  be  held  in  place  not 
less  than  24  hours.     Under  such  loads  there  shall  be  no  deflection  of  slabs  or  beams  exceeding 
1/800   of   the   span,  nor   any  other  indication  of  weakness  in  any  part  of  the  structure. 

11.  When  necessary  to  make  tests  on  concrete  less  than  sixty  days  old,  the  test  load  shall  be 
reduced  to  an  amount  proportionate  to  the  strength  at  the  age  tested,  the  proper  reduction  to  be 
determined  by  the  Engineer  in  charge. 

12.  In  event  of  failure  of  any  part  of  the  structure  under  test,  the  Engineer  may  require 
tests  to  be  made  of  all  such  other  parts  as  he  may  deem  advisable,  the  expense  of  such  tests  to 
be  borne  by  the  Contractor. 

13.  The  Engineer  may,  at  his  discretion,  apply  a  test  load  equivalent  to  the  specified  live 
load,  at  full  speed,  instead  of  the  static  test  load  described  herein. 

14.  In  case  the  structure,  or  any  part  thereof,  does  not  meet  satisfactorily  the  tests  specified 
herein,  the  Contractor  shall  remove  and  replace  all  such  defective  work  at  his  own  expense. 

46 


Watson's   Bridge   Specifications  Section  XVI 


Retaining  Walls,  Abutments,  Piers,  Etc. 


1.  In  the  design  of  reinforced  concrete  retaining  walls,  the  lateral  pressure,  due  to  the  back 
filling,  shall  be  ascertained  by  means  of  Rankine's  method  of  analysis,  assuming  the  weight  of 
ordinary  earth  fill  as  equal  to  100  Ibs.  per  cubic   foot.     The  resultant  of  the  lateral  pressure  shall 
be  assumed  to  act  at  a  point  one-third  the  height  of  the  wall  from  the  base. 

2.  In  the  case  of  massive  concrete  vertical  retaining  walls,  the  width  of  the  footing  should 
not  be  less  than  30%  of  the  height  for  walls  not  surcharged   to   40%    for   walls   which    are   sur- 
charged, for  hard  foundations.     For  walls  which  carry  heavy  electric  railway  or  steam  railroad 
traffic,  the  ratio  of  width  of  footing  to  height  of  walls  shall  never  be  less  than  four-tenths. 

3.  For  reinforced  concrete  retaining  walls,  the  same  relation  of  width  of  footing  to  height 
of  wall,  as  given  above,  may  be  used,  provided  that  approximately  one-third  of  the  width  of  the 
footing  lies  in  front  of  the  abutment  and  two-thirds  to  the  rear.     When  a  greater  proportion 
than  this  is  in  the  rear  of  the  abutment,  the  ratio  of  depth  to  height  must  be  increased. 

4.  Whenever  the  material  back  of  a  retaining  wall  is  subject  to  saturation  with  water,  the 
wall  must  be  designed  to  resist  the  full  theoretical  hydraulic  pressure. 

5.  Instead  of  Rankine's  theory,  retaining  walls  may  be  computed  by  means  of  the  use  of  an 
equivalent  fluid  pressure  which  may  be  taken  at  from  13  to  33  Ibs.  per  cubic  foot,  according  to 
the  nature  of  the  material  and  the  nature  of  the  surcharge  load. 

6.  In  using  Rankine's  theory  for  retaining  walls  which  are  used  to  support  a  non-surcharged 
fill,  but  which  are  subject  to  use  as  abutments  for  railroad  bridges  or  other  structures  carrying 
heavy  loads  upon  the  top  of  the  back  fill,  such  walls  shall  always  be  computed  as  though  support- 
ing a  surcharged  fill,  equivalent  in  weight  to  the  live  load. 

7.  In  the  design  of  mass  concrete  retaining  walls  and  similar  structures,  expansion  joints 
shall  be  provided  at  intervals  not  exceeding  50  feet.     This  distance  may  be  increased  if  longi- 
tudinal reinforcement  be  used  and  walls  may  be  built  without  expansion  joints  if  the  ratio  of  the 
longitudinal  reinforcing  steel  to  the  area  of  the  concrete  equals  or  exceeds  1/2  of  \%. 

8.  Sea  walls  or  other  retaining  walls  which  may  be  subjected  to  saturation  of  the  back  fill 
shall  be  proportioned  to  resist  the  fluid  pressure  due  to  the  action  of  a  fluid  equal  in  weight  to  the 
weight  of  the  filling  material. 

9.  Sea  walls  subject  to  wave  action  shall  be  proportioned  to  resist  the  pressure  of  a  head  of 
water  equal  to  twice  the  greatest  wave  height. 

10.  Sea  walls  and  all  other  concrete  construction  in  salt  water  shall  be  composed  of  a  dense 
waterproof,  rich  mixture,  and  the  cement  shall  be  one  which  shall  have  shown  its  fitness  for  use 
in  salt  water.     Whenever  practicable,  all  concrete  exposed  to  the  action  of  the  sea  water  shall  be 
cast  and  set  in  air  before  placing. 

11.  All  abutments  shall  be  designed  to  resist  the  thrust  of  the  backing  in  combination  with 
the  direct  vertical  loads  and  horizontal  forces  (due  to  tractive  forces,  etc.),  without  exceeding 
the  specified  unit  stresses. 

12.  In  assuming  the  angle  of  repose  of  the  back  filling,  a  slope  of  one  vertical  to  one  and 
one-half  horizontal  shall  be  assumed  for  loose  dry  earth  or  sand  and  a  slope  of  one  to  one  for 
carefully  laid  and  compacted  dry  earth  filling. 

47 


Watson's  Bridge   Specifications  Section  XVI 

13.  All  abutments  shall  be  carefully  drained  by  means  of  tile  carried  through  the  wall,  with 
the  openings  at  the  back  carefully  protected  by  broken  stone. 

14.  The  faces  of  abutments  and  piers  shall  be  given  a  batter,  unless  otherwise  shown  on 
the  plans,  of  %  inch  to  the  foot,  and  there  shall  be  provided  a  coping  course  under  the  bridge 
seat  in  the  case  of  abutments  for  steel  bridges,  which  shall,  unless  otherwise  shown  on  the  plans, 
be  16  inches  deep  and  project  4  inches. 

1,5.  Back  walls  for  abutments  of  steel  bridges  shall  have  a  thickness  at  the  base  of  at  least 
60%  of  their  height  for  Classes  A,  B,  C  and  D,  and  50%,  for  all  other  classes,  or  else  be 
reinforced. 

16.  Unless  otherwise  specified,  concrete  for  abutments  shall  be  mixed  in  the  proportion  of 

1  part  Portland  Cement,  2*/2  parts  sand  and  5  parts  broken  stone   (No.  7^)   for  massive  con- 
crete, and  imbedded  stone  (rubble  concrete)  may  be  used  if  so  indicated  on  the  drawing  or  per- 
mitted (in  writing)  by  the  Engineer  in  charge. 

17.  Concrete  for  bridge  seats  shall  be  No.  5   mix,   composed   of   1   part   Portland   cement, 

2  parts  hard  sand  and  3  parts  hard  stone. 

18.  All  anchor  bolts  for  steel  superstructure,  when  used,  shall  be  furnished  by  the  Owner 
and  set  by  the  Contractor. 

19.  All  abutments  and  retaining  walls  shall  have  all  surfaces  in  contact  with  earth  fill  water- 
proofed, using  coal  tar  pitch  as  specified  for  dampproofing  in  Section  XI,  unless  otherwise  called 
for  on  the  drawings. 

20.  The  mixtures  to  be  used  in  concrete  piers  shall  be  the  same  as  those  used  in  abutments. 

21.  The  pressure  of  ice  against  concrete  piers  shall  be  considered  and  shall  be  taken  as 
equal  to  the  water  line  on  the  exposed  side  multiplied  by  the  maximum  depth  of  ice  for  that 
latitude  and  multiplied  by  1,000  Ibs.  per  square  foot. 

22.  Piers  shall  also  be  proportioned  to  withstand  impact  from  floating  logs  or  other  forces 
to  which  they  may  probably  be  subjected. 


48 


Watson's  Bridge  Specifications  Section  XVII 


Concrete  Arches 


1.  All  arches  shall  be  computed  and  proportioned  in  accordance  with  the  regulations  given 
under  Sections  II  and  III,  and  complete  stress  diagrams,   using  an  approved  method  of  elastic 
analysis,  must  accompany  all  plans. 

2.  All  arches  shall  be  assumed  to  be  subject  to  a  range  of  temperature  of  +35°  Fahr.  for 
latitude  40.    The  limit  shall  be  increased  for  higher  and  decreased  for  lower  latitudes  and  pro- 
vision shall  be  made  for  expansion  and  contraction  due  to  this  change  at  the  crown  and  at  the 
piers.    The  effect  of  the  shortening  of  the  arch  ring,  due  to  axial  compression,  shall  be  taken 
fully  into  account. 

3.  Unless  otherwise  indicated,  the  following  proportions  shall  be  used  in  arch  construction: 

(a)  For  the  arch  ring,   light  spandrel  walls,  light  spandrel  arches,  etc.,  one  part  Portland 
cement,  two  parts  sand  and  four  parts  stone  (Mix  No.  6). 

(b)  For  heavy  spandrel  walls,  light  piers  and  wing  walls,  one  part  Portland  cement,  two  and 
one-half  parts  sand  and  five  parts  stone  (Mix  No.  7^). 

(c)  For  heavy  piers,  wing  walls,  etc.,  of  massive  concrete,  one  part  Portland  cement,  two 
and  one-half  parts  sand  and  five  parts  stone  (Mix  No.  7^),  in  which  may  be  imbedded  25%  of 
large  stones. 

(d)  For  heavy  footings  of  massive  concrete,  one  part  Portland  cement,  three  parts  sand 
and  six  parts  stone  (Mix  No.  9),  in  which  may  be  imbedded  25 %  of  large  stones,  or  Mix  No.  6 
may  be  used  with  Puzzulan  cement. 

4.  In  general  the  arch  rings  of  concrete  arches  shall  be  laid  in  transverse  sections,  laying 
the  crown  section  first,  then  the  sections  at  the  quarter  points  and  filling  in  between.     The  vous- 
soirs  thus  formed  shall  be  provided  with  keys  equal  in  depth  to  one-fourth  the  depth  of  the  arch 
ring. 

5.  The  crown  thickness  of  reinforced  arches  shall  be  not  less  than  one-sixtieth  of  the  span, 
nor  the  thickness  at  the  springing  point  less  than  one  and  one-half  times  the  crown  thickness. 

6.  The  reinforcing  steel  for  reinforced  concrete  arches  shall  not  be  less  than  ^  of  1%  of 
the  section  at  the  crown. 

7.  The  spandrel  walls  shall  be  securely  anchored  to  the  arch  rings  by  means  of  proper 
dowels,  and  the  arch  ring  reinforced  transversely  sufficiently  to  provide  for  the  maximum  lateral 
thrust  on  the  spandrel  walls. 

8.  All  earth  covered  arches  shall  be  waterproofed  on  all  surfaces  in  contact  with  the  filling 
material. 

9.  In  case  hinged  arches  are  used,  the  hinges  shall  preferably  be  of  annealed  cast  steel, 
imbedded  as  much  as  practicable  in  the  concrete  and  effectively  anchored  thereto. 

10.  In  case  ribbed  arches  are  used  each  rib  shall  be  considered  as  a  beam  to  resist  the 
bending  stresses  and  the  thrust,  and  in  case  full  spandrel  braced  concrete  arches  are  used,  the 
spandrels  shall  be  considered  only  as  assisting  in  the  resistance  to  bending  and  the  rib  shall  be 
sufficiently  strong  to  resist  the  direct  thrust.     In  the  case  of  full  spandrel  braced  arches  the  span 
and  rise  may  be  taken  as  the  span  and  rise  of  the  intrados,  and  the  non-elastic  theory  be  used  in 
computing. 

49 


Watson's   Bridge    Specifications  Section  XVII 

11.  Arches  shall  be  fully  analyzed  by  methods  of  analysis  based  upon  the  elastic  theory  of 
the  arch  and  at  least  two  conditions  of  live  load  shall  be  assumed. 

First:   The  live   load   covering  the   entire  arch. 

Second:  Live  load  covering  one-half  the  arch.  For  arches  over  100  feet  in  span,  positions 
of  the  live  load  giving  maximum  stresses  at  critical  sections  shall  be  determined. 

The  method  developed  by  Prof.  Cain  (Van  Nostrand  Science  Series)  is  recommended  or 
Principles  of  Reinforced  Concrete  Construction  by  Turneaure  &  Maurer. 

12.  All  arch  rings  shall  be  of  sufficient  thickness  so  that  the  resultant  line  of  pressure  as 
found  by  the  methods  prescribed  in  the  preceding  article  will  not  pass  outside  of  the  middle  third 
of  the  arch  ring  or  else  they  shall  be  reinforced. 

13.  The  fill  over  arches  shall  be  thoroughly  compacted,  and  shall  not  be  placed  in  less  than 
two  weeks  after  the  completion  of  the  arch  ring. 


50 


Watson's   Bridge    Specifications  Section  XVIII 

Reinforced  Concrete  Slabs,  Beams,  Girders,  Columns 

and  Trusses 


1.  Reinforced  concrete  for  slab,  beam,  girder  and  column  construction  and  for  all  other 
types  of  reinforced  concrete  construction  shall,  unless  otherwise  specified,  be  proportioned  as 
follows : 

For  carefully  screened  stone  or  gravel  concrete,  1  part  Portland  cement,  2  parts  sand  and 
4  parts  broken  stone  (Mix  No.  6). 

For  slag  concrete,  1  part  Portland  cement,  2  parts  sand  and  4  parts  No.  1  slag  (Mix  No.  6). 
All  materials  are  to  be  of  the  quality  and  sizes   as   herein   described. 

2.  The  sizes  of  broken  stone  or  slag  for  use  in  reinforced  concrete  slab,  beam,  girder  and 
column  work  shall  not  exceed  1  inch  for  large  work  nor  %  inch  for  small  work. 

3.  When  reinforced  concrete  columns  are  exposed   to   probable   injury  by   vehicles,   etc., 
they  shall  be  protected  for  a  height  of  4  feet  from   the   ground,   preferably   by   metal    forms   of 
structural  steel  or  cast  iron. 

4.  When  through  girders  or  beams  carry  slabs  or  beams  attached  near  the  lower  edge,  they 
shall  be  provided  with  stirrups  at  such  points  sufficient  to  carry  the  applied  load  to  the  upper  part 
of  the  girder,  such  stirrups  to  be  suitably  anchored  to  the  slab  or  beam  or  other  satisfactory  pro- 
vision shall  be  made. 

5.  Provision  shall  be  made  for  expansion  at  distances  not  greater  than  100  feet  apart  in  all 
slab,  beam  and  girder  construction  when  the  reinforcement   in    such    direction   is   not   less   than 
1/2  of  1%  of  the  concrete  section,  and  at  less  distance  when  the  reinforcement  is  less.  For  concrete 
not  reinforced  continuously  in  two  directions,  expansion  joints  shall  be  provided  at  distances  not 
exceeding  50  feet  apart  in  the  direction  in  which  the  concrete  is  not  reinforced. 

6.  Reinforced  concrete  trusses  shall  be  designed  in  such  a  manner  that  the  tensile  stresses 
will  be  entirely  resisted  by  the  steel  and  the  compressive  stresses,  as   far  as  practicable,  by  the 
concrete. 

7.  As  far  as  possible,  they  shall  have  no  eccentric  connections,  and  the  tension  bars  must  be 
anchored  at  the  connections  in  such  a  way  as  to  develop  their  full  stress  without  producing  bend- 
ing moment  about  the  joints,  unless  such  moments  be  carefully  determined  and  provided  for. 

8.  In    general,    reinforced    steel    construction  for  trusses  will  be  preferrd  to  reinforced 
concrete. 

9.  Concrete  used  for  trusses  of  reinforced  concrete  or  reinforced  steel  shall  not  be  leaner 
than  1-2-4  and  preferably  should  be  1-1^-3  with    maximum    size    of    stone    not    greater    than 
24  inch.    Unless  otherwise  specified,  these  latter  proportions  will  be  required. 


51 


Watson's   Bridge    Specifications  Section  XIX 


Foundations  and  Footings 


1.  The  hydraulic  uplift  of  water  penetrating  underneath  the  footings  of  piers  and  abutments 
shall  be  considered. 

2.  All  footings  shall,  wherever  practicable,  be  laid  free  from  water  and  no  concrete  foot- 
ings shall  be  laid  in  water  except  by  special  arrangement  with  the  Engineer. 

3.  Footings  having  heads  of  piles  imbedded  therein  shall  have  the  contents  of  the  imbedded 
piles  deducted  in  computing  contents  of  masonry. 

4.  Reinforced  concrete  footings  shall  be  designed  in  accordance  with  the  provisions  of  pre- 
ceding sections,  but  no  reinforcement  shall  be  placed  at  a  less  distance  than  8^/2  inches  from  any 
concrete  surface.     When  the  footing  is  submerged,  or  in  wet  ground,  the  reinforcement  shall  be 
protected  by  not  less  than  4  inches  of  concrete. 

5.  The    reinforcement    shall    be    so    arranged  as   to   distribute  the   loads   equally   on   the 
foundation. 

6.  Reinforced  concrete  footings  shall  always  be -1-2-4  (No.  6)  mix  Portland  cement  con- 
crete, and   Mass  concrete  footings   shall  be  1-2^-5  (No.  7*/i)  mix  concrete,  unless  otherwise 
shown  on  the  drawings.     (See  Paragraph  3,  Section  I). 

NOTE. — A  mat  of  reinforcing  bars  in  the  bottom  of  a  mass  concrete  footing,  used  as  ties  and 
not  to  resist  bending  stresses,  shall  not  be  considered  as  changing  the  classification  of  the  con- 
crete to  reinforced  concrete. 

7.  In  estimating  the  excavation  for  footings,  the  size  of  excavations  shall  be  taken  as  equal 
to  the  neat  size  of  the  footings,  plus  one  foot  all  around,   with   sides  vertical,   and  no   allowance 
shall  be  made  for  additional  excavation,  unless  so  stated  in  the  contract. 

8.  Unless  otherwise  agreed  upon,  the  price  bid  by  the  Contractor  for  the  footings  shall 
includb  all  sheeting,  pumping,  cofferdams,  bracing,  etc.,  required  to  keep  the  pits  open  and  free 
from  water  while  depositing  concrete,  the  removal  of  same,  and  backfilling  to  the  original  level 
of  the  ground. 

9.  When  permanent  timber  sheet  piling  is  called  for  on  the  plans,  it  shall  be  built  as  shown 
thereon,  and  paid  for  per  foot  board  measure  of  timber  in  place.     In  general,  timber  sheet  piling 
shall  be  left  in  place  around  piers  in  streams  or  other  places  subject  to  scour. 

10.  When  Wakefield  sheet  piling  is  called  for,  it  shall  be  triple  lap,  of  thickness  as  indicated 
on  plans,  bolted  at  intervals  of  not  over  six  feet  with  two  bolts,  and  spiked  at  intermediate  points 
not  over  18  inches  apart.     Bolts  shall  be  ^  inch  for  three  inch  piling,  ^  inch  for  six  inch  and 
Y%  inch  for  9  and  12  inch  thicknesses.    The  thickness  called  for  shall  be  assumed  to  be  based  upon 
the  theoretical  thickness  of  plank  before  planing.     The  middle  plank  shall  be  surfaced  two  sides. 
The  tongue  shall  be  not  less  in  width  than  the  thickness  of  the  plank. 

11.  When  permanent  steel  sheet  piling  is  called  for  on  the  plans,  it  shall  be  of  the  size  and 
type  shown  thereon,  and  paid  for  per  pound  in  place. 

12.  When  temporary  steel  sheet  piling  is  shown  on  the  plans,  and  the  cost  is  not  included 
in  the  excavation,  it  shall  be  paid  for  per  square  foot  of  piling  driven,  and  shall  be  removed 
without  extra  charge. 

52 


Watson's   Bridge    Specifications  Section  XIX 

13.  When  permanent  concrete  sheet  piling  is  called  for,  it  shall  be  constructed  and  driven 
as  indicated  on  the  plans,  and  paid  for  per  square  foot  in  place. 

14.  When  cofferdams  are  required,  they  shall,  unless  otherwise  specified,  be  paid  for  on  a 
lump  sum  basis,  to  include  construction,  maintenance  and  removal,  including  pumping  when 
required. 

lo.     All  foundations  shall  be  carried  to  a  depth  well  below  the  frost  line,  or  possible  scour. 

16.     No  concrete  shall  be  laid  on  any  foundation  until  such   foundation  shall  have  been 
inspected  and  accepted  by  the  Engineer  in  charge. 


53 


Watson's   Bridge    Specifications  Section   XX 

Timber  Piling 


1.  No.  1  grade  timber  piles  shall  be  of  white,  burr  and  post  oak;  Southern  yellow  pine; 
Douglas  fir;  tamarack;  Eastern  white  and  red  cedar;    chestnut;    Western    cedar;    redwood    or 
cypress. 

2.  No.  2  grade  piles  shall  include  red  and  all  other  oaks  not  included  in  the  No.  1   grade ; 
sycamore ;  sweet,  black  and  tupelo  gum ;  maple ;  elm ;  hickory ;  Norway  pine,  or  any  sound  timber 
that  will  stand  driving. 

3.  Piles  shall  be  cut  from  sound  trees ;  shall  be  close  grained  and  solid,  free  from  defects, 
such  as  injurious  ring  shakes,  large  and  unsound  or  loose  knots,  decay  or  other  defects,  which 
may  materially  impair  their  strength  or  durability.    In  Eastern  red  or  white  cedar  a  small  amount 
of  heart  rot  at  the  butt,  which  does  not  materially  injure  the  strength  of  the  pile,  will  be  allowed. 

4.  Piles  must  be  cut  above  the  ground  swell  and  have  a  uniform  taper  from  butt  to  tip. 
Short  bends  will  not  be  allowed.    A  line  drawn  from  the  center  of  the  butt  to  the  center  of  the 
tip  shall  lie  within  the  body  of  the  pile. 

5.  Unless  otherwise  specified,  piles  must  be  cut  when  the  sap  is  down.     No.  1  grade  piles 
shall  be  peeled  soon  after  cutting.    All  knots  shall  be  trimmed  close  to  the  body  of  the  pile. 

6.  For  round  piles  the  minimum  diameter  at  the  tip  shall  be  nine  inches  for  lengths  not 
exceeding  30  feet;  eight  inches  for  lengths  over  30  feet,  but  not  exceeding  50  feet  and  seven 
inches  for  lengths  over  50  feet.    The  minimum  diameter  at  one-quarter  of  the  length  from  the 
butt  shall  be  12  inches  and  the  maximum  diameter  at  the  butt  20  inches. 

7.  For  square  piles  the  minimum  width  of  any  side  of  the  tip  shall  be  nine  inches  for  lengths 
not  exceeding  30  feet;  eight  inches  for  lengths  over  30  feet,  but  not  exceeding  50  feet,  and  seven 
inches  for  lengths  over  50  feet     The  minimum  width  of  any  side  at  one-quarter  of  the  length 
from  the  butt  shall  be  12  inches. 

8.  No.  1  grade  square  piles  shall  show  at  least  80%  heart  on  each  side  at  any  cross  section 
of  the  stick,  and  round  piles  shall  show  at  least  10^  inches  diameter  of  heart  at  the  butt. 

9.  The  bearing  capacity  of  timber  piles  shall  be  based,  unless  otherwise  specified,  upon  the 
following  formula : 

P  =  s5+^h  where  P  =  total  safe  load  on  pile  in  pounds,  W  =  weight  of  hammer  in 

pounds,  h  =  fall  of  hammer  in  feet  and  S  =  average    penetration    for    last    foot    in 

inches. 

When  a  steam  hammer  is  used  P  =  g'V^i  where  W  =    weight  of   striking  parts  of 

hammer  in  pounds  and  the  other  symbols  are    the    same    as    given  above   for  drop 

hammers.  * 

10.  When  driving  is  done,  or  assisted,  by  water  jet,  the  hammer  shall  be  used  to  test  the 
bearing  of  the  pile  after  the  jetting  is  completed. 

11.  The  Engineer  may  require  the  use  of  the  steam  hammer  instead  of  the  drop  hammer, 
whenever,  in  his  opinion,  there  is  a  possibility  of  damage  to  adjoining  work  by  the  impact  of 
driving. 

54 


Watson's   Bridge    Specifications  Section   XX 

12.  Piles  shall  not  be  pointed  when  driven  into  soft  material,  and  may  be  pointed  to  a  six- 
inch  square  for  driving  in  ordinary  material. 

13.  Steel  or  cast  iron  shoes  shall  be  provided  for  piles  when  driving  in  very  hard  material, 
as  shall  be  required  by  the  Engineer  in  charge. 

14.  Steel  bands  shall  be  provided  whenever  necessary  to  prevent  brooming  the  head  of  the 

pile. 

15.  Driving    caps    shall  be    provided    when,    in    the    opinion    of   the    Engineer,   they   are 
necessary. 

16.  Timber  piles  shall  be  paid  for  at  the  contract  prices  for  piling  furnished  and  for  piling 
driven. 

17.  Tops  of  piles  shall  be  sawed  off  true  and  level  at  elevations  shown. 

18.  In  general,  timber  piles  for  foundations  shall  be  spaced  not  to  exceed  two  feet  six  inches 
apart,  shall  be  not  less  than  12  feet  in  length  in  firm  ground  and  30  feet  in  soft  ground,  shall  be 
embedded  in  the  concrete  footings  at  least  six  inches,  and  the  load  carried  shall  not  exceed  20 
tons  per  pile. 

19.  No  reliance  shall  be  placed  upon  vertical  timber  piles  to  resist  horizontal  thrust. 


55 


Watson's   Bridge    Specifications  Section    XXI 


General 


1.  Specifications  given  on  drawings  shall  supersede  requirements  given  herein  for  the  par- 
ticular structure  for  which  such  drawings  are  made. 

2.  rln  estimating  quantities  of  reinforced  concrete,  no  deduction  shall  be  made  for  the  volume 
occupied  by  the  reinforcing  rods. 

3.  Concrete  structures  built  on  the  Unit  system,  in  which  the  several  parts  are  molded  sepa- 
rately and  erected  into  place,  shall  be  subject  to  all  the  restrictions  given  herein,  the  same  as 
for  monolithic  construction.    When  proper  provision  is  made   for  bonding  unit  slabs  into  unit 
beams  and  girders,  the  usual  assumption  for  the  "T"  beams  may  be  used.     When  members  are 
made  on  a  jarring  machine,  or  similar  device,  to  increase  the  strength  of  the  concrete,  the  unit 
stresses  used  may  be  increased  proportionately  to  the  increased  strength,  the  percentage  of  increase 
to  be  determined  by  the  Engineer  in  charge. 

4.  Expansion  joints  in  concrete  work  shall  be  provided  at  all  points  where  cracks  would 
naturally  occur  and  in  mass  concrete,  walls,  etc.,  shall,  in  general,  be  spaced  not  to  exceed  50  feet 
apart.     In  reinforcing  to  provide  against  cracking,  due  to  contraction  of  concrete,  the  amount 
of  reinforcement  provided  shall  be  not  less  than  %  of  1%  of  the  concrete  area.    Expansion  joints 
shall  be  provided  with  concrete  keys.    Between  the  surfaces  there  shall  be  placed  at  least  two 
thicknesses  of  asbestos  board,  ^5  inch  thick,  or  other  satisfactory  separators. 

5.  The  royalty  for  all  patented  constructions  shown  on  the  plans,  or  called  for  in  the  specifi- 
cations, shall  be  paid  by  the  Owner,  except  when  such  plans  and  specifications  are  prepared,  or 
submitted,  by  the  Contractor,  in  which  case  all  royalties  are  to  be  paid  by  the  Contractor. 

6.  The  royalty  for  all  patented  devices  used  by  the  Contractor  in  the  execution  of  the  work 
or  for  patented  details  used  by  the  Contractor,  but  not  shown  or  called  for  on  the  drawings, 
shall  be  paid  by  the  Contractor. 

7.  The  party  responsible  for  the  payment  of   royalties   for  the   use  of   patents  shall   also 
defend  any  and  all  suits  that  may  be  brought  for  infringement  of  such  patents  and  shall  pay  all 
damages  arising  from  such  suits  to  either  the  Owner  or  the  Contractor. 

8.  Patented  construction  shown  on  plans  shall  be  so  designated  thereon,  giving  the  number 
of  the  patent  and  indicating  the  part  of  the  design  which  is  covered  thereby,  and  the  Contractor 
shall  not  knowingly  use  a  patented  device  in  construction  without  notifying  the  Owner. 

9.  When  anchor  bolts  or  other  devices  are  to  be  placed  in  concrete,  they  shall,  unless  other- 
wise specified,  be  placed  by  the  Contractor  for  the  concrete  work,  who  shall  notify  the  Owner 
at  least  one  week  in  advance  of  such  placing.     All  anchor  bolts  or  other  devices  to  be  imbedded 
in  the  concrete,  which  are  not  part  of  the  concrete  work,  shall,  unless  otherwise  arranged,  be 
furnished  by  the  Owner. 


56 


Watson's   Bridge    Specifications  Section  XXII 


Cement  Walks,  Concrete  Curbs  and  Roadways 


1.  Portland  cement  walks  on  bridges  shall,  in  general,  consist  of  a  reinforced  concrete  slab 
base  with  a  wearing  course,  one  inch  thick,  of  rich  mortar.    The  slab  base  shall  be  computed  to 
sustain  the  actual  dead  and  the  required  live  loads,  in  accordance  with  preceding  sections  of  these 
specifications.     Expanded  metal,  woven  or  welded  wire  mesh  will  be  preferred  for  the  reinforce- 
ment of  sidewalk  slabs.     The  wearing  course  shall  be  one  inch  thick,  and  shall  be  placed  as  soon 
as  possible  after  the  base,  but  not  more  than  45  minutes  thereafter.    The  wearing  course  shall  con- 
sist of  one  part  cement  to  two  parts  crushed  stone,  carefully  selected  for  greatest  resistance  to 
abrasion,  well  graded  in  size,  passing  a  ^  inch  screen,  and  held  on  a  No.  30  sieve.    The  Engineer 
in  charge  may,  at  his  discretion,  allow  a  selected  sand,  conforming  in  size  to  the  crushed  stone 
specified,  to  be  used..     The  sidewalk  surface  shall,  unless  otherwise  noted,  have  a  slope  of  ^  inch 
to  the  foot.    Sidewalk  surfaces  shall  have  all  corners  rounded  to  y?.  inch  radius.     The  wearing 
course  shall  be  of  the  proper  consistency  to  work  well  with  a  wood  float. 

2.  When  the  sidewalk  finish  cannot  be  laid  at  the  same  time  as  the  slab,  the  finish  coat  shall 
be  two  inches  thick  and  the  base  shall  be  carefully  cleaned,  scored,  soaked  with  water  and  painted 
with  a  cement  grout  immediately  before  placing  the  finish. 

3.  When  one  course  walks  are  specified,  the  entire   slab   shall   be   composed  of  one  part 
cement,  two  parts  selected  sand  and  three  parts  crushed   stone,   and   immediately   finished  as 
specified  above  for  two  course  work. 

4.  All  sidewalks  of  Portland  cement  shall  be   finished   by   workmen   especially  skilled   in 
the  art. 

o.  Portland  cement  sidewalks  on  approaches  to  bridges  will  not  usually  be  considered  part 
of  the  bridge  contract,  but  when  they  are  so  specified,  they  shall  be  built  with  a  surface  .finish 
similar  to  that  described  for  sidewalks  on  the  bridge,  laid  on  a  base  prepared  as  follows : 

The  sub-grade  surface  shall  be  12  inches  below  finished  grade,  thoroughly  compacted  by 
rolling  or  tamping  and  well  drained.  On  this  shall  be  laid  a  course  of  broken  stone,  gravel  or 
cinders  six  inches  in  thickness,  after  rolling  with  a  roller  weighing  not  less  than  five  tons  or 
compacting  with  a  rammer  weighing  not  less  than  50  Ibs.  on  a  surface  of  100  square  inches.  No 
material  over  four  inches  in  size  shall  be  used  in  the  foundation  thus  prepared.  Upon  this 
foundation  shall  be  laid  the  concrete  walk  with  a  thickness  of  six  inches. 

6.  If  a  two  course  walk  be  specified,  the  first  course  shall  be  five  inches  thick,  of  1-2^-5 
(No.  71/2 )  concrete,  using  1^4  inch  to  ^4  mch  coarse  aggregate.     The  wearing  course  shall  be 
placed  and  proportioned  as  above  specified  for  concrete  slabs  on  bridges.    If  one  course  work  be 
specified,  the  entire  thickness  of  six  inches  shall  be  composed  of  1-2-3  (No.  5)  concrete  as  before 
specified. 

7.  Expansion  joints  in  cement  walks  shall  be  placed  at  intervals  of  not  over  30  feet,  unless 
the  walks  be  reinforced. 

8.  Cement  walks  shall  be  divided  into  blocks  containing  not  more  than  36  square  feet,  and 
not  more  than  six  feet  in  any  dimension,  or  else  reinforcement  shall  be  provided  of  a  cross-section 
of  not  less  than  0.041  square  inch  per  square  foot. 

9.  Concrete  curbs  on  bridges  shall  be  laid  at  the  same  time  as  the  sidewalk  slabs,  and  when 
combined  curbs  and  gutters  are  specified,  the  gutters  shall  be  poured  integral  with   the   curbs. 
All  proportions,  materials,  finish,  etc.,  of  concrete  curbs  shall  be  same  as  specified  for  walks. 

57 


Watson's    Bridge    Specifications  Section   XXII 

10.  The  thickness  of  curbs  shall  be  not  less  than  six  inches  and  all  curbs  shall  be  battered 
one  inch  in  eight  inches.    The  edge  of  curb  next  to  roadway  shall  be  rounded  to  1l/2  inch  radius, 
unless  metal  protection  strip  be  specified.    The  corner  between  curb  and  gutter  shall  be  rounded 
to  1^  inch  radius  and  all  other  corners  to  y*  inch  radius. 

11.  Expansion  joints  shall  coincide  with  expansion  joints  in  sidewalks  and  roadway. 

12.  Concrete  curbs  on  fills  over  arches  and  on  approaches  shall  be  not  less  than  six  inches 
thick  at  top  and  12  inches  thick  at  base,  and  24  inches  deep,  laid  on  a  foundation  course  of  com- 
pacted gravel,  broken  stone,  cinders,  or  slag,  not  less  than  six  inches  thick. 

13.  Combined  curbs  and  gutters  on  fill  over  arches  or  on  approaches  shall  be  not  less  than 
six  inches  thick  at  top  and  12  inches  thick  at  base,  and  the  width  of  gutter  shall  be  not  less  than 
16  inches  nor  more  than  24  inches.     Such  curbs  and  gutters  shall  be  laid  in  sections,  from  five 
to  eight  feet  in  length,  on  a  compacted  base  of  cinders,  gravel  or  broken  stone  or  slag,  and  all 
proportions,  method  of  laying,  etc.,  shall  be  the  same  as  specified  for  cement  walks.    The  back- 
fill for  curbs  shall  be  composed  of  the  same  material  as  the  base. 

14.  The  radius  of  curb  at  all  street  intersections  shall  be  six  feet  unless  otherwise  specified. 

15.  Walks  and  curbs  shall  be  kept  wet  by  sprinkling  and  covered  with  canvas  or  other  suit- 
able material  for  a  period  of  at  least  four  days. 

16.  When  concrete  sidewalks  or  curbs  are  laid  on  a  newly  placed  fill,  which  exceeds  two 
feet  in  depth,  there  shall  be  provided  metal  reinforcement  placed  %  inch  in  from  the  under  side 
of  the  slab  and  two  inches  from  the  under  side  of  the  curb,  the  area  of  such  reinforcement  to  be 
not  less  than  1/200  of  the  cross  sectional  area  of  the  concrete. 

17.  Two  course  concrete  pavement  shall  be  constructed  in  the  following  manner : 

If  on  filled  material,  the  fill  shall  be  deposited  in  layers  of  one  foot  thickness,  compacted  by 
rolling  with  a  roller  weighing  not  less  than  five  tons,  or  by  ramming  with  a  hand  tamper  weighing 
not  less  than  50  Ibs.  on  100  square  inch  area. 

If  pavement  is  to  be  built  in  cut,  the  sub-grade  shall  be  thoroughly  rolled  or  compacted  as 
above  described. 

18.  On  the  sub-grade  thus  prepared,  lay  the  first  course,  six  inches  thick,  of  1-2^-4  con- 
crete, using  y-2,  inch  stone,  first  wetting  the  surface  of  the  sub-grade. 

19.  The  second  or  wearing  course  shall  be  two  inches  thick  and  shall  be  laid  on  the  first 
course  within  45  minutes  after  the  first  course  is  poured,  and  shall  consist  of  one  part  cement  to 
one  part  selected  sand  and  1^  parts  crushed  stone,  especially  selected  for  resistance  to  abrasion, 
and  composed  of  ^  to  %  inch  material,  not  more  than  10%  being  allowed  to  pass  a  %  inch 
screen.    This  stone  shall  contain  no  soft,  flat  or  elongated  particles. 

20.  All  concrete  pavements  shall  be  crowned  not  more  than  1/100  of  the  width,  with  trans- 
verse joints  not  more  than  36  feet  apart,  shall  be  screeded  to  grade,  floated  with  wood  float  and 
kept  wet  and  protected  from  the  weather  by  canvas  or  other  suitable  material  for  at  least  ten  days, 
and  shall  be  closed  to  traffic  for  at  least  fourteen  days  in  favorable  weather. 

21.  Joints  shall  be  %  mcn  wide,  filled  with  prepared  bitumen  saturated  expansion  strips 
and  protected  by  soft  steel  plates  not  less  than  %y2  inches  wide  and  %  inch  thick,  curved  to  crown 
and  thoroughly  anchored  into  the  concrete. 

22.  All  pavements  over  20  feet  wide  shall  be  reinforced  with  metal  placed  two  inches  below 
the  top  surface,  and  having  not  less  than  0.05  square  inches  of  metal  per  foot  of  section  each 
way. 

58 


Watson's   Bridge    Specifications  Section  XXII 

23.  Drains  and  catchbasins  shall  be  located  as  indicated  on  plans. 

24.  If  the  curb  be  integral  with  the  pavement,  use  the  same  proportion  as  specified  for  the 
pavement  for  the  curb  base,  and  use  the  wearing  course  mixture  for  that  part  of  the  curb  above 
the  base. 

25.  If  one  course  pavement  be  specified,  the  mixture  shall  be  1-2-3,  using  specially  selected 
sand  and  1%  inch  stone,  containing  no  soft,  flat  or  elongated  particles.     The  thickness  shall  be 
not  less  than  six  inches  and  all  preceding  requirements    for   two   course   pavement   in   regard   to 
preparation  of  sub-grade,  finish,  joints,  etc.,  shall  be  observed. 

26.  Scuppers,  catchbasins,  downspouts  and  drains  shall  be  furnished  and  placed  as  shown 
on  drawings.     Scuppers  and  catchbasins  shall  be  of  cast  iron,  not  less  than  y^  inch  thick,  free 
from  defects,  and  subject  to  hammer  testing  for  soundness  and  toughness.       Downspouts  and 
drains  shall  be  of  cast  or  wrought  iron.     All  shall  be  heavily  coated  with  asphaltum  fluxed  with 
residuum  oil,  or  such  other  protective  coating  as  may  be  specified. 

27.  Curbs  on  bridges  and  approaches  thereto  shall  be  eight  inches  high,  unless  otherwise 
specified. 


Watson's   Bridge    Specifications  Section   XXIII 


Brick  Pavement 


1.  When  so  shown  on  the  plans,  the  roadways  of  bridges  or  bridge  approaches  shall  be 
paved  with  brick. 

2.  All  materials  shall  be  carefully  excavated  to  a  sub-grade  uniformly  below  the  required 
surface  of  the  finished  pavement,  allowing  for  the  depth  of  the  brick,  one  inch  sand  cushion,  and 
six  inches  of  concrete.    All  soft,  or  unsuitable  material   below  the   sub-grade   shall   be  removed. 
Excavation  or  shrinkage  below  the  sub-grade  shall  be  filled  with  1-3-6  (No.  9)  concrete,  which 
shall  form  a  part  of  the  concrete  foundation  specified  below.    When  the  pavement  is  to  be  laid 
on  embankments,  the  filling  shall  be  made  in  layers  of  about  six  inch  thickness,  compacted  by 
ramming  or  rolling,  or  other  means  satisfactory  to  the  Engineer. 

3.  Upon  the  subgrade  shall  be  laid  and  thoroughly  rammed  for  the  full  width  between  curbs 
a  layer  of  1-3-6  (No.  9)  concrete  not  less  than  six  inches  in  depth  at  any  point,  unless  otherwise 
indicated  on  the  plans. 

4.  Upon  the  concrete  foundation,  prepared  as  specified,  shall  be  placed  a  cushion  of  sand  of 
such  thickness  that,  after  the  brick  are  firmly  bedded  by  rolling,  the  upper  surface  thereof  shall 
be  exactly  at  the  required  grade  and  the  sand  cushion  shall  be  about  1%  inches  thick.     The 
cushion  shall  consist  of  sand,  stone  dust  or  granulated  slag,  passing  a  %  inch  screen.    The  sand 
cushion  shall  be  compressed  by  rolling  with  a  hand  roller  of  about  300  Ibs.  weight.     The  cushion 
is  to  be  rolled,  depressions  filled,  and  rerolled  not  less  than  three  times.    The  sand  shall  be  slightly 
wet  at  the  time  the  brick  are  laid. 

5.  Upon  the  sand  cushion  shall  be  laid  vitrified  paving  bricks  of  best  quality,  sound,  hard 
burned,  of  uniform  size,  well  formed,  all  from  one   manufactory,    all    of    one    color,    made   and 
burned  especially  for  street  pavements.     They  shall  be  homogeneous  in  character  and  compact  in 
structure,  free  from  lumps  of  uncrushed  clay  or  injurious  lamination,  fire  cracks  or  checks  of 
more  than  a  superficial  extent  and  when  immersed  in  water  for  four  days  they  shall  not  develop 
cracks  nor  spall. 

6.  When  dried  for  24  hours  at  a  temperature  of  not  less  than  212°  Fahr.  and  then  imme- 
diately immersed  in  water  for  24  hours,  no  brick  shall  absorb  more  than  3%  of  its  weight. 

7.  No  paving  brick  shall  crush  under  a  load  of  10,000  Ibs.  per  square  inch  when  tested  on 
edge. 

8.  The  bricks  shall  be  laid  on  edge  at  right  angles   to  the   street  or   as   directed  by  the 
Engineer.     Each  alternate  course  shall  commence  with  a  half  brick,  but  half  bricks  or  bats  shall 
not  be  used  except  at  the  ends  of  courses. 

9.  All  longitudinal  joints  shall  be  broken  with  a  lap  of  not  less  than  three  inches.    The  joints 
shall  be  laid  tight  and  all  bricks  shall  be  laid  by  skilled  workmen  who   shall   stand  on  the  brick 
already  laid.    In  no  case  shall  the  sand  bed  be  disturbed  after  being  brought  to  the  exact  sub- 
grade  and  crown  of  the  street. 

10.  After  the  bricks  are  laid,  they  shall  be  rolled  to  the  proper  surface  with  a  roller  weigh- 
ing not  less  than  five  tons. 

11.  The  entire  surface  shall  be  closely  inspected,  brick  by  brick,  by  a  skilled  workman, 
who  shall  remove  any  brick  which  may  be  found  chipped  or  broken,  irregular  in  shape,  not  a 
perfect  fit,  or  not  to  exact  surface,  and  who  shall  remedy  such  defective  spots  if  found. 

60 


Watson's   Bridge   Specifications  Section   XXIII 

12.  The  joint  next  to  the  curb  shall  be  one  inch  wide  and  filled  before  the  balance  of  the 
roadway  is  grouted  with  bituminous  cement  which  must  not  run  at  a  temperature  of  100°  Fahr., 
nor  become  brittle  at  0°  Fahr.    A  similar  transverse  joint  shall  be  made  at  all  expansion  joints  in 
bridges  and  over  the  crown  of  all  arches. 

13.  The  entire  surface  shall  finally  be  flushed  and  the  joints   filled  with   Portland  cement 
grout  in  the  following  manner :  First,  a  pure  thin  grout  shall  be  formed  of  one  part  cement  to  one 
of  clean,  fine,  sharp  sand,  passing  a  No.  10  sieve,  and  the  whole  surface  shall  be  flushed  with 
this  from  a  portable  grout  box,  care  being  taken  to   fill   all  the  joints.     Afterwards  a  thicker 
grout,  formed  of  the  same  proportions  of  cement  and  sand  with  just  enough  water  to  enable  it  to 
run,  shall  be  forced  into  the  joints  and  the  pavement  shall  then  be  completely  covered  with  sand 
and  left  undisturbed'  for  not  less  than  eight  days  before  being  thrown  open  to  traffic.    Before  the 
final  acceptance  of  the  work,  the  Contractor  shall    sweep    the    street    clean    and    remove    the 
sweepings. 

14.  The  top  surface  of  the  finished  pavement  shall  conform  accurately  to  the  grades  and 
pitch  to  be  given  by  the  Engineer. 

15.  When  brick  pavement  is  laid  on  bridges,  the  floor  of  which  forms  a  base  for  same,  the 
sand  cushion  shall  be  laid  directly  on  such  base. 

16.  The  contract  price  of  brick  pavement  shall  include  the  cost  of  all  labor  and  materials 
required  to  prepare  the  subgrade,  lay  the  concrete  foundation,  sand  cushion  and  the  brick  surface 
as  specified  in  the  preceding  paragraphs.     Payment  will  be  made  for  the  actual  number  of  square 
yards  of  brick  pavement  measured  in  place. 

17.  When  "T"  rails  are  laid  in  brick  pavement,  special  shaped  brick  shall  be  used  on  gage 
side  of  rails,  and  care  shall  be  taken  to  insure  that  all  spaces  between  rails  and  bricks  be  filled 
with  cement  mortar. 

18.  The  Contractor  must  file  sample  brick  with  his  bid  or  else  must  name  some  well  known 
brand  which  he  will  use. 

19.  For  operations  not  covered  by  these  specifications,  the  Standard1  Specifications  of  the 
National  Paving  Brick  Manufacturers  Association  shall  be  followed. 


61 


Watson's   Bridge    Specifications  Section   XXTV 


Asphalt  Block  Pavement 


1.  The  blocks  shall  be  standard  size  (usually  five  inches  in  width  by  twelve  inches  in  length). 
Unless  otherwise  specified,  blocks  shall  be  two  inches  in  depth.     A  variation   %   of  an  inch 
from  these  dimensions  will  be  sufficient  ground  for  rejecting  any  block. 

2.  The  blocks  shall  be  composed  of  the  following  materials : 

Asphaltic  Cement  _ 9  to  13% 

Conglomerate  copper  sand  (see  note) 76  to  62% 

Limestone  Dust  15  to  25  % 

3.  The  copper  sands  in  the  blocks  must  be  brushed  so  that  every  particle  will  pass  a  screen  of 
^  inch  mesh.     The  blocks  must  receive  a  compression  in  the  molds  of  not  less  than  220  tons, 
and  must  weigh  not  less  than  10  Ibs.  per  block.     The  blocks  shall  yield,  when  extracted  with 
bisulphide  of  carbon  and  after  the  evaporation  of  the  solvent,  not  less  than  6%,  or  more  than  8% 
of  bituminous  matter. 

NOTE. — Other  sands  may  be  used  subject  to  the  approval  of  the  Engineer. 

4.  The  asphaltic  cement  shall  be  composed  of   steam   refined   Trinidad   Lake   asphalt   and 
heavy  petroleum  oil,  or  other  equally  good  flux.     The  refined  asphalt  and  the  flux  shall  be  mixed 
in  such  proportions  as  will  produce  an  asphaltic  cement  of  a  proper  consistency  and  quality.    The 
heavy  petroleum  oil  shall  be  free  from  impurities  and  brought  to  a  specific  gravity  of  from 
10°  to  14°  Beaume  and  shall  have  a  fire  test  of  not  less  than  350°   Fahr. ;  it  shall  contain  an 
appreciable  amount  of  light  oils  or  matter  volatile  under  250°  Fahr.,  and  the  distillate  at  400° 
Fahr.  for  30  hours  shall  be  less  than  10%.    Any  other  flux,  if  used,  as  a  substitute  for  the  heavy 
petroleum  oil,  shall  also  fulfill  the  above  tests  except  that  for  specific  gravity. 

5.  Upon  the  surface  of  the  cement  foundation  shall  be  spread  a  bed  of  cement  mortar 
i/2  inch  in  thickness.    This  mortar  bed  shall  be  composed  of  Portland  cement  and  sand,  as  speci- 
fied, and  mixed  in  the  proportion  of  one  part  cement  to  four  parts  sand.    This  mortar  bed  shall 
be  "struck,"  by  an  approved  method,  to  a  true  surface  exactly  parallel  to  the  top  of  the  finished 
pavement  and  the  depth  of  the  block  below  it. 

6.  Upon  this  mortar  bed  the  blocks  shall  be  immediately  laid  with  close  joints  and  uniform 
top  surface. 

7.  The  blocks  shall  be  laid  by  the  pavers  standing  upon  the  blocks  already  laid,  and  not 
upon  the  bed  of  mortar. 

8.  The  blocks  shall  be  laid  at  right  angles  with  the  line  of  the  street  with  such  crown  as  the 
Engineer  may  direct;  and  in  such  manner  that  all  longitudinal  joints  shall  be  broken  by  a  lap  of 
at  least  four  inches.     The  blocks  shall  be  so  laid  as  to  make  the  lateral  joints  as  tight  as  possible, 
consistent  with  keeping  a  good  alignment  of  the  courses  across  the  street  and  the  longitudinal 
joints  shall  be  immediately  closed  by  pressing  each  course  in  the  direction  of  its  length  by  lever. 
When  thus  laid  the  blocks  shall  be  immediately  covered  with  clean,  fine  dry  sand,  entirely  free 
from  any  loam  or  earthy  matter.     This  sand  shall  be  swept  over  the  surface  until  the  joints  are 
all  filled  and  shall  be  allowed  to  remain  on  the  pavement  not  less  than  thirty  days  or  for  such 
length  of  time  as  will  allow  the  street  traffic  to  thoroughly  grind  the  sand  into  all  the  joints. 

9.  The  price  bid  per  square  yard  of  asphalt  block  surface  must  include  the  laying,  and  fur- 
nishing of  all  materials,  labor  and  implements  necessary  to  complete  the  wearing  surface,  includ- 
ing the  mortar  bed,  as  specified  above. 

62 


Watson's   Bridge    Specifications  Section   XXIV 

10.  When  asphalt  block  pavements  are  laid  on  filled  or  natural  foundations  requiring  a  sub- 
base,  the  base  shall  be  prepared  as  follows : 

All  materials  shall  be  carefully  excavated  to  a  sub-grade  uniformly  below  the  required  sur- 
face of  the  finished  pavement,  allowing  for  the  depth  of  the  block,  one  inch  sand  cushion  and  six 
inches  of  concrete.  All  soft  or  unsuitable  material  below  the  sub-grade  shall  be  removed. 
Excavation  or  shrinkage  below  the  sub-grade  shall  be  filled  with  1-3-6  (No.  9)  concrete,  which 
shall  form  a  part  of  the  concrete  foundation  specified  below. 

Upon  the  sub-grade  shall  be  laid  and  thoroughly  rammed  for  the  full  width  between  curbs  a 
layer  of  1-3-6  (No.  9)  concrete,  not  less  than  six  inches  in  depth  at  any  point.  To  mark  the  top 
grade  of  the  concrete,  sound  stones  of  suitable  size  and  depth  shall  be  set  upon  the  sub-grade  about 
12  feet  apart  along  the  center  and  each  side  of  the  roadway  as  the  Engineer  may  direct.  Such 
marking  stones  shall  remain  and  form  a  part  of  the  concrete  foundation. 

11.  When  the  plans  call  for  the  asphalt  block  to  be  laid  on  a  cushion,  sand,  stone  dust  or 
granulated  slag,  passing  a  %  inch  screen,  shall  be  used,  slightly  wet,  and  carefully  screeded  to 
grade.     All  other  work  shall  conform  to  that  specified  for  block  laid  directly  on  the  concrete. 


63 


Watson's   Bridge    Specifications  Section   XXT 


Sheet  Asphalt  Pavement 


1.  Sheet  asphalt  pavements  on  bridges  shall  generally  be  laid  upon  a  concrete  or  asphalt 
binder  base,  which  in  the  case  of  buckle  plate  floor  construction   shall   never   be  less  than   1% 
inches  thick  over  the  heads  of  projecting  rivet  heads  and  buckles. 

2.  When  asphalt  pavements  are  laid  upon  concrete  sub-base  the  surface  shall  be  carefully 
cleaned  and  roughened  and  a  neat  cement  or  other  binding  material  be  placed  thereon  and  the 
asphalt  binder  and  wearing  surface  to  the  depth  of  %l/2  inches  shall  be  immediately  placed  thereon. 

3.  The  pavement  shall  be  equal  in  all  respects  to  the  best  grade  of  standard  asphalt  pave- 
ment which  is  being  built  by  any  established  paving  company  at  the  time  the  pavement  herein 
described  is  built. 

4.  When  asphalt  pavement  is  called  for  on  filled  approaches  or  other  filled  constructions, 
the  said  fill  shall  be  carefully  excavated  or  graded  to  a  subgrade  8y2  inches  below  the  required 
surface  of  the  finished  pavement.    All  soft  or  unsuitable  material  below  the  subgrade  shall  also 
be  removed  and  any  excavation  below  the  subgrade   shall   be   filled   with   concrete   or   carefully 
tamped  sand,  gravel  or  broken  stone. 

5.  Upon  the  subgrade  shall  be  laid  a  thoroughly  rammed  layer  of  concrete  (1-3-6),  not  less 
than  six  inches  in  depth.     Upon  this  concrete  base  shall  be  laid  the  asphalt  binder  and  wearing 
surface,  2,l/2  inches  thick. 

6.  The  2%  inch  asphalt  pavement  shall  be  composed  of  two  courses,  the  binder  course  and 
the  pavement  mixture  or  wearing  surface. 

7.  The  binder  course  shall  be  composed  of  clean,  broken  stone,  gravel  or  slag  of  such  size 
as  will  pass  through  a  one-inch  ring. 

8.  The  asphalt  cement  shall  be  composed  of  300  Ibs.  of  asphalt  and  about  18  Ibs.  of  heavy 
oil ;  the  quantity  of  oil  will  vary  as  may  be  necessary  to  produce  the  best  results. 

9.  The  broken  stone,  gravel  or  slag  shall  be  heated  and  thoroughly  mixed  with  asphaltic 
cement  in  such  proportions  as  shall  thoroughly  coat  the  particles  of  stone,  gravel  or  slag. 

]  0.     The  mixture  shall  be  spread  on  the  foundations  to  such  a  thickness  that,   after  being 
compacted  by  a  roller  weighing  not  less  than  five  tons,  it  shall  have  a  thickness  of  one  inch. 

11.  The  pavement  mixture  shall  be  laid  immediately  upon  the  binder  course.     It  shall  be 
brought  to  the  work  at  a  temperature  of  250°  Fahr.     It  shall  then  be  carefully  spread  by  means 
of  iron  rakes  in  such  manner  as  to  give  a  uniform  and  regular  grade  and  to  such  depth  that 
after  having  received  its  ultimate  compression,  it  shall  have  a  thickness  of  two  inches.    The  sur- 
face shall  then  be  compressed  by  a  hand  roller,  after  which  a  small  amount  of  cement  shall  be 
swept  over  it  and  it  shall  then  be  thoroughly  compressed  by  a  heavy  steam  roller,  the  rolling  being 
continued  as  long  as  it  makes  an  impression  on  the  surface. 

12.  Asphalt  shall  not  be  laid  directly  against  Street  Railway  Tracks,  but  special  shaped  pav- 
ing block,  in  full  lengths  and  half  lengths  alternating,  shall  be  laid  alongside  the  rails,  and  filled 
with  asphaltic  cement,  unless  other  details  are  shown  on  the  drawings. 

13.  This  paving  block  shall  be  equal  to  that  specified  for  brick  paving  and  will  be  paid  for 
at  the  same  rate  as  asphalt  paving. 

64 


Watson's   Bridge    Specifications  Section   XXV 

14.  Next  to  the  curb  the  pavement  shall  be  coated  over  with  pure  hot  asphalt  for  a  width 
of  15  inches  after  the  paving  is  completed. 

15.  The  composition  of  the  pavement  mixture  shall  be  from  12  to  16  parts  of  asphaltic 
cement  mixed  with  67  to  73  parts  of  clean,  sharp  sand  and  from  15  to  17  parts  of  pulverized  car- 
bonate of  lime. 

16.  The  sand  and  asphaltic  cement  shall  be  heated  separately  to  about  300°  Fahr. 

17.  The  pulverized  carbonate  of  lime  while  cold  shall  be  mixed  with  the  hot  sand  in  the 
required  proportions  and  shall  then  be  mixed  with  the  asphaltic  cement  at  the  required  tempera- 
ture and  in  the  required  condition  with  an  apparatus  suited  to  affect  a  perfect  mixture. 

18.  The  asphaltic  cement  shall  be  composed  of  100  parts,  by  weight,  of  refined  asphalt 
mixed  with  12  to  15  parts  of  heavy  petroleum  oil. 

19.  Asphalt  pavement  shall  be  laid  only  by  workmen  experienced  in  that  class  of  work.    If 
a  guarantee  is  required,  the  Owner  will  deduct  and  retain  from  the  final  estimate  or  other  esti- 
mates, an  amount  equal  to %  of  the  amount  due  for  paving,  which  money  will  be  retained  for 

a  period  of years,  and  if  at  the  end  of years  the  Contractor  shall  have  made  good  all 

defects  which  may  have  developed  in  the  paving,  the  Owner  will  return  to  the  Contractor  the 
amount  so  retained. 

20.  Expansion  joints  must  be  provided  in  the  base  wherever  shown  on  the  plans. 

21.  When  the  asphalt  pavement  is  laid  directly  upon  concrete  floor  plates  of  bridges,  the 
base,  as  specified  above,  shall  be  omitted  and  only  the  2^2  inch  thick  pavement  be  required. 

22.  The  price  bid  per  square  yard  of  sheet  asphalt  surface  shall  include  the  laying,  furnish- 
ing of  all  materials,  labor  and  implements  necessary  to  complete  both  base  and  finished  surface. 


65 


Watson's   Bridge   Specifications  Section   XXVI 


Wood  Block  Pavement 


1.  On  the  concrete  floor  slab  shall  be  laid  a  dry  sand  and  cement  cushion,  composed  of  one 
part  of  a  slow  setting  Portland  cement  and  four  parts  clean,  dry  sand,  thoroughly  mixed  before 
spreading,  and  after  spreading  shall  be  surfaced  and  then  rolled  to  the  correct  crown  and  grade. 
The  cushion,  after  compacting,  shall  not  be  less  than  y2  inch. 

2.  As  the  block  is  laid,  the  layer  of  sand  and  cement  shall  be  moistened  by  sprinkling  and 
the  block  laid  immediately  after  sprinkling,  in  order  that  the  cement  will  not  have  an  opportunity 
to  set  before  the  blocks  are  placed.    The  blocks  shall  then  be  laid  at  right  angles  to  the  length  of 
the  bridge,  in  parallel  lines,  grain  vertical,  and  adjoining  courses  breaking  joints  not  less  than  three 
inches.    Two  lines  of  block,  next  to  each  curb  and  next  to  each  rail,  shall  be  laid  with  long  dimen- 
sion of  block  parallel  to  curb ;  the  balance  of  the  blocks  to  be  at  right  angles  to  these.     Blocks 
shall  not  be  laid  in  contact.    Transverse  joints  shall,  unless  otherwise  specified,  be  %  inch  open 
joints,  and  longitudinal  joints  shall  be  %  inch.    Satisfactory  mechanical   spacing  devices  shall  be 
provided  to  secure  uniform  width  of  joints. 

3.  Along  the  curb  lines,  on  both  sides  of  the  roadway,  for  the  entire  length  of  the  bridge, 
shall  be  provided  an  expansion  joint,  one  inch  thick,  of  the  depth  of  the  paving  block,  and  trans- 
verse joints  %  inch  thick  shall  be  provided  across  the  roadway  at  the  ends  and  approximately 
50  feet  apart  for  the  entire  length  of  the  bridge,  or  as  shown  on  plans.     These  joints  shall  be 
made  by  placing  boards  of  the  proper  thickness  in  position  to  hold  the  block  in  place  until  ready 
for  filler.    The  boards  shall  then  be  removed  carefully  and  the  joints  filled  with  a  bituminous 
filler,  as  specified.     At  expansion  joints  in  the  bridge   structure,   the   transverse   joints   shall   be 
sufficient  to  provide  for  the  maximum  possible  movement  of  the  joint. 

4.  The  fitting  and  piecing  of  blocks  along  the  sides  and  ends  shall  be  neatly  and  carefully 
done  and  as  the  Engineer  directs.    No  piecing  will  be  allowed  except  along  sides  and  ends  and 
all  irregular,  uneven  or  unsatisfactory  block  shall  be  removed. 

5.  After  the  block  have  been  laid,  they  shall  be  properly  rolled  or  tamped  to  a  firm  bearing 
and  uniform  surface.     All  blocks  which  are  defective,  broken,  split  or  otherwise  damaged  or 
displaced,  shall  be  removed  immediately  after  rolling  or  tamping  and  replaced  with  sound  blocks. 
Blocks  should  be  inspected  as  carefully  as  possible  before  laying  and  rolling,  in  order  that  the 
blocks  may  not  be  disturbed  after  rolling  unless  necessary. 

6.  After  the  block  have  passed  the  inspection  of  the  Engineer,  the  joints  between  blocks  and 
the  expansion  joints  shall  be  filled  to  two-thirds  the  depth  of  block  with  a  bituminous  filler,  accept- 
able to  the  Engineer.    The  filler  shall  not  become  brittle  at  0°  Fahr.  nor  flow  at  120°  Fahr. 

7.  The  paving  filler  shall  be  heated  and  flushed  into  the  joints  to  two-thirds  the  depth  of  the 
block,  and  poured  at  a  temperature  at  which  it  is  so  liquid  that  it  will  run  freely  into  the  joints 
and  in  no  case  at  a  temperature  of  less  than  300°  Fahr. 

8.  After  the  first  has  set,  a  second  coat  shall  be  applied  to  complete  all  unfilled  joints  to  the 
proper  height.    The  filling  of  the  joints  shall  be  done  only  in  clear  dry  weather  when  the  tempera- 
ture of  the  air  is  not  less  than  50°  Fahr.    While  the  last  application  is  still  hot,  a  l/$  inch  layer 
of  clean,  coarse,  dry  sand  shall  be  spread  over  and    rolled    into    the    entire    surface,    filling   the 
balance  of  the  joints. 

9.  The  wood  block  shall  be  purchased  from  a  reputable  firm  engaged  in  creosoting  timber ; 
said  firm  to  be  satisfactory  to  the  Engineer. 

66 


Watson's   Bridge    Specifications  Section   XXVI 

10.  If,  for  any  reason,  the  blocks  cannot  be  laid  within  a  reasonable  time  after  treatment, 
they  shall  be  piled  closely  and  covered  to  protect  them  from  the  weather. 

11.  The  wood  from  which  the  blocks  are  made  must  be  of   Southern  Yellow  pine  of  the 
grade  known  as  Prime  Timber.     All  timber  must  be  sound,  well  manufactured,  all  square  edge, 
and  free  from  the  following  defects :  unsound,  loose  and  hollow  knots,  worm  and  knot  holes  or 
other  defects  which  will  be  detrimental  to  the  life  of  the  block  or  interfere  with  its  laying.     No 
second  growth  timber  will  be  allowed.     The  annual  rings  shall  average  not  less  than  eight  and 
there  shall  not  be  less  than  six  to  any  one  inch,  measured  radially  from  the  heart. 

12.  The  blocks  shall  average  80%  and  no  blocks  shall  contain  less  than  50%  of  heart  wood. 
The  blocks  shall  be  from  six  to  ten  inches  long  (except  the  necessary  number  of  shorter  blocks  to 
break  joints),  but  shall  average  eight;  their  depth  (parallel  to  fibre)  shall  be  of  the  depth  speci- 
fied, but  not  less  than  three  inches,  and  their  width  shall  be  from  three  to  four  inches,  but  all 
blocks  used  in  any  one  contract  shall  be  of  the  same  width.   The  blocks  shall  be  truly  rectangular, 
smoothly  and  evenly  sawn  and  of  uniform  dimensions.    The  depth  may  not  vary  more  than^  inch 
from  that  specified. 

13.  The  blocks  shall  be  treated,  preserved  or  creosoted  as  hereinafter  specified    and    each 
block  shall  contain  at  least  16  Ibs.  of  creosote  oil  per  cubic  foot  of  wood  or  when  a  block  con- 
tains much  natural  pitch,  it  shall  receive  as  much  creosote  as  can  be  forced  into  it  by  the  same 
process  and  pressure  as  is  used  in  the  treatment  of  the  blocks  of  the  same  kind  of  wood  which  will 
receive  16  Ibs.  of  creosote  oil  per  cubic  foot. 

14.  The  creosote  oil  shall  be  a  dead  oil  or  coal  tar  product.     It  shall  not  contain  more  than 
3%  of  water  and  if  it  does  contain  this  amount  of  water,  a  corresponding  correction  must  be  made 
so  that  an  equivalent  additional  amount  of  creosote  is  forced  into  the  blocks.    It  shall  contain  only 
traces  of  acetic  acid  and  acetates.     Its  specific  gravity  at  100°  Fahr.   (38°  C.)   shall  be  at  least 
1.03  and  not  more  than  1.07  so  as  to  assure  its  thoroughly  penetrating  the   wood  blocks.      The 
residue  insoluble  by  filtration  with  benzol  and  chloroform  must  not  exceed  3%  of  the  weight  of 
the  creosote  oil.    Fractional  distillation  of  100  grams  of  the  creosote  oil  shall  produce  percentages 
of  dry  oil  by  weight  within  the  following  limits : 

Up  to       150°  C.  (302°  F.) Not  to  exceed  2% 

Between  150°  C.  (302°  F)  and  170°  C.    (338°   F.) "  1.5% 

170°  C.  (338°  F.)  and  235°  C.    (455°   F.) "  35% 

235°  C.  (455°  F.)  and  300°  C.    (572°   F.) _           "  35%, 

15.  The  residue  remaining  shall  be  soft  and  adhesive.    The  creosote  oil  shall  contain  about 
25%  of  crystalizable  napthalene  and  at  least  15%  anthracene  oils.     At  least  95%  of  the  creosote 
oil  shall  be  soluble  in  carbon-bisulphide  and  equally  in  absolute  alcohol. 

16.  The  wood  blocks,  after  being  cut  and  ready  for  treatment,  shall  be  placed  in  a  suitable 
iron  receptacle  or  cylinder  and  there  sterilized  with  dry  steam  under  a  pressure  of  at  least  30  Ibs. 
and  not  to  exceed  50  Ibs.  per  square  inch  during  at  least  three  hours  and  as  much  longer,  not  to 
exceed  seven  hours,  as  the  condition  of  the  wood  and  the  season  of  the  year  requires.    The  tem- 
perature within  the  cylinder  during  the  process  of  steaming  shall  be  between  200°  and  240°  Fahr. 
At  intervals  during  this  process,  the  condensed  steam,  sap  and  other  liquid  matter  shall  be  drawn 
from  the  receptacle  by  means  of  valves.    At  the  completion  of  the  steaming  process,  all  condensed 
steam  and  other  fluid  matter  shall  be  blown  from  the  cylinder  through  an  opening  in  its  bottom, 
and  the  steam  shall  be  caused  to  pass  out  through  an  opening  in  its  top. 

17.  The  draining  and  exhaust  valves  of  the  cylinder  shall  then  be  closed  and  a  vacuum  pump 
shall  immediately  produce,  as  quickly  as  possible,  a  vacuum  of  at  least  24  inches  and  as  much 

67 


Watson's  Bridge  Specifications  Section   XXVI 

more  as  may  be  necessary,  and  maintained  in  the  cylinder  until  moisture  and  gases  cease  to  come 
from  the  cylinder.  During  this  process  the  wood  blocks  within  the  cylinder  shall  be  kept  hot 
by  means  of  steam  coils  within  it. 

18.  Immediately  thereafter  and  while  the  vacuum  exists,  the  creosote  oil  at  a  temperature 
between  180°  Fahr.  and  200°  Fahr.  shall  be  run  into  the  cylinder  and  forced  and  maintained 
under  such  pressure  that  the  wood  blocks  shall  absorb  and  be  impregnated  with  creosote  oil  to 
the  amount  specified  above.    The  excess  of  creosote  oil  in  the  cylinder  shall  then  be  withdrawn; 
the  blocks  drained  and  prepared  for  shipment. 

19.  The  blocks  ready  for  use  must  meet  the  following  indentation  pressure  test,  which  may 
be  made,  at  the  discretion  of  the  Engineer,  to  replace  the  requirements  of  Paragraphs  11  and  12. 

The  blocks  to  be  tested  are  first  dried  at  100°  Fahr.  during  12  hours.  Then  a  polished  steel 
die  of  one  square  inch  on  its  lower  face,  square  edges,  corners,  and  perpendicular  sides,  is  placed 
on  a  dried  block,  firmly  supported  in  a  compression  machine.  A  pressure  of  8,000  Ibs.  is  applied 
quickly  and  maintained  exactly  one  minute.  The  die  must  not  descend  and  indent  the  block 
more  than  ^  inch.  The  measurements  are  to  be  taken  from  when  the  die  is  lightly  pressed 
against  the  block  to  the  instant  the  8,000  Ibs.  pressure  has  been  applied  one  minute.  The  die  is 
placed  anywhere  within  %  inch  of  the  edges  of  the  block  and  so  as  to  compress  lengthwise  the 
wood  fibres. 

20.  The  wood  blocks  shall  be  inspected  by  the  Engineer  at  the  place  of  manufacture  or  on 
arrival  at  the  point  where  they  are  to  be  used  or  when  piled  adjacent  to  the  street  to  be  paved. 
All  blocks  not  in  conformity  with  the  requirements  of  these  specifications  will  be  rejected  and 
shall  be  removed  from  the  locality  of  the  pavement  to  be  laid. 

21.  Alternate  proposals  will  also  be  received  on  Lug  or  special  shaped  blocks,  which  shall, 
so  far  as  possible,  comply  with  the  above  specifications.     Such   alternate  proposals   shall   be  on 
the  regular  form  of  proposal. 

22.  When  wood  block  pavements  are  laid  on  approaches  or  fill,  a  concrete  base  shall  be 
provided  as  specified  for  brick  pavements. 

23.  The  price  bid  for  wood  block  pavements  shall  include  all  labor  and  materials  required 
to  complete  the  work,  including  the  concrete  base,  when  required. 


68 


Watson's  Bridge  Specifications  '  ,   '      j  " '  {    '  5*ct}c«;  XJfYIl 

Bituminous  Pavement 


1.  The  concrete  base  shall  be  dry,  thoroughly  cleaned  of  all  laitance,  dirt,  grease  and  loose 
materials.     It  shall  preferably  be  given  a  rough  finish,  either  by  leaving  coarse  aggregate  at  the 
surface  or  by  brooming,  or  otherwise  mechanically  roughening  the  surface  of  the  green  concrete. 
On  this  base  shall  be  laid  the  bituminous  wearing  surface,  two  inches  in  thickness,  as  follows : 

2.  The  aggregate  shall  be  composed  of  gravel  or  hard  crushed  stone,  passing  a  one  inch 
screen  with  the  dust  screened  out.     To  this  shall  be  added  sufficient  sand,  from  one-quarter  to 
one-half  the  volume  of  the  stone,  according  to  the  character  of  the  stone.     This  sand  shall  be 
clean,  hard,  preferably  silicious,  and  at  least  25%,  shall  be  retained  on  a  screen  having  20  meshes 
per  inch  and  5%  shall  pass  a  screen  having  80  meshes  per  inch. 

3.  The  aggregate  shall  be  heated  to  a  temperature  of  325°  Fahr.  for  Binder  "a,"  120°  to 
200°  for  Binder  "b"  and  Binder  "c,"  when  the  bituminous  cement  at  the  proper  temperature  and 
in  the  proper  proportion  shall  be  added. 

4.  The  bituminous  cement  shall  be  composed  of  one  of  the  following  materials,  or  a  similar 
product  approved  by  the  Engineer  in  charge. 

(a)  Standard  Paving  Asphalt    (manufactured  by  the  Standard  Oil  Company  of  New  Jersey) 
not  less  than  22  gallons  to  the  cubic  yard  of  aggregate,  applied  at  a  temperature  of  not  less  than 
350°  Fahr. 

(b)  Bermudez  Road  Asphalt   (The  Barber  Asphalt  Paving  Co.)  not  less  than  17  nor  more 
than  20  gallons  to  the  cubic  yard  of  aggregate,  applied  at  a  temperature  of  not  less  than  300° 
or  more  than  375°  Fahr. 

(c)  Tarvia  X   (The  Barrett  Company)  not   less    than    15    gallons   to   the    cubic   yard   of 
aggregate,  heated  to  a  temperature  of  from  200  to  300°  Fahr. 

5.  The  aggregate  and  binder  shall  be  thoroughly  mixed  by  hand  with  warm  shovels,  or  in 
a  suitable  machine.     Hand  mixing  will  be  allowed  only  when  the  quantity  is  less  than  200  square 
yards. 

6.  The  mixture  shall  be  applied  hot  to  the  concrete  surface  and  spread  by  means  of  hot  hoes 
or  rakes,  screeded  to  the  proper  thickness  and  thoroughly  rolled  with  a  roller  weighing  not  less 
than  five  tons. 

7.  A  finish  coat  shall  then  be  applied  to  the  surface  of  the  pavement,  consisting  of  a  seal 
coat  of  the  hot  bituminous  material,  followed  by  an  application  of  stone  screenings,  or  fine  sand 
where  screenings  are  not  obtainable,  passing  a  %  inch  screen  and  free  from  fine  dust. 

8.  The  bituminous  finish  shall  stop  at  the  gutter  line,  and  the  gutter  be  finished  with  a  two 
inch  cement  finish,  mixed  in  the  proportion  of  one  part  Portland  cement  to  two  parts  hard,  clean 
sand,  or  screenings,  and  carefully  trowelled  to  surface  and  grade. 

9.  The  bituminous  finish  shall  not  be  laid  next  to  steel  rails,  but  a  course  of  creosoted  wood, 
stone  or  brick  paving  shall  always  be  used  adjacent  to  such  rails. 

10.  Bituminous  pavement  shall  be  estimated  by  the  square  yard. 

11.  The  Engineer  in  charge  may  require  any  one  of  the  above  specified  materials  to  be 
used  on  any  particular  job  and  the  Contractor  shall  not  place  order  for  same  until  such  order  is 
approved  by  the  Engineer.    The  Engineer  may  modify  the  quantities  given  in  these  specifications 

69 


W.itfon'-?  Rri<?£e  Specifications  3  Section  XXVIT 

to  meet  the  requirements  of  the  particular  aggregate  to  be  used.  The  Engineer  may  also,  at  his 
discretion,  require  the  surface  of  the  concrete  base  to  be  swabbed  with  hot  bituminous  cement 
before  placing  the  two  inch  finish. 

12.  The  Engineer  in  charge  may,  at  his  discretion,    require    the    use    of    the    "Penetration 
Method"  for  small  areas  when  a  mixing  machine  is  not  available,  instead  of  the  mixing  method 
herein    described.      Hand    sprinkling   pots    of    approved   design   shall   be  used   to  distribute  the 
bitumen. 

13.  When  bituminous  pavements  are  specified  for  approaches  or  on  fills,  a  concrete  base 
shall  be  provided,  the  same  as  specified  for  brick  pavements. 

14.  The  price  bid  for  bituminous  pavements  shall  include  all  labor  and  materials  required 
to  complete  the  work,  including  the  concrete  base,  when  required,  except  that  an  extra  price 
shall  be  bid  for  swabbing  the  base  with  bituminous   cement,   if   required   as   specified   in   Para- 
graph 11. 


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